A reinterpretation of human breast anatomy includes all the layers of the anterior body wall.

Mammary glands define mammals as a group, yet a comprehensive anatomical description of the mammary gland does not exist for almost any mammalian species. In humans, the anatomical and surgical literature provide conflicting and incomplete descriptions of the gross anatomy of the breast. We dissected 9 male and 15 female human body donors to clarify this gross anatomy. We found that, like other epidermally derived glands of the body, the mammary glandular tissue is constrained to a membrane-bound, central structure referred to as the corpus mammae in the surgical literature, and not dispersed throughout the breast as typically described in the anatomical literature. The major fasciae of the human anterior body wall, including the superficial fatty Camper's fascia and the deeper membranous Scarpa's fascia, both contribute to the structure of the breast. This anatomical arrangement suggests that, as the mammary gland invaginates posteriorly from the integument during embryological development, the mammary fat pad most likely derives from Camper's fascia, and growth of Scarpa's fascia around this fat pad forms the anterior and posterior lamellae of the breast pocket. Anteriorly, Scarpa's fascia becomes a double layer that creates the surface structure of the breast. Posteriorly, Scarpa's fascia forms a circummammary ligament that (1) stabilizes the breast against the thoracic wall and (2) is continuous with Scarpa's fascia on the rest of the anterior body wall. The suspensory ligaments of the breast represent the typical retinaculae cuti found consistently throughout the human body wall, and do not directly attach to the skin. Instead, these retinaculae attach to the anterior or posterior lamella of Scarpa's fascia.

Comparative anatomy of the felid brachial plexus reflects differing hunting strategies between Pantherinae (snow leopard, Panthera uncia) and Felinae (domestic cat, Felis catus).

The brachial plexus, a network of ventral rami providing somatic sensory and motor innervation to the forelimb, is of particular importance in felids. Large-bodied pantherines require powerful rotatory and joint stabilizing forelimb muscles to maintain secure holds on large prey, while smaller-bodied felines are small prey specialists reliant on manual dexterity. Brachial plexus dissections of two snow leopards (Panthera uncia) and two domestic cats (Felis catus) revealed that generally the morphology of the brachial plexus is quite conserved. However, differences in the nerves supplying the shoulder and antebrachium may reflect differing prey capture strategies between the subfamilies. The brachial plexus of both species derives from ventral rami of C6-T1. In P. uncia, an extensive musculus (m.) subscapularis with multiple pennations is innervated by a larger number of nn. subscapulares, deriving from more spinal cord levels than in F. catus. C6 continues to become n. suprascapularis in both taxa; however, in F. catus, it also gives branches that join with C7, while in P. uncia, it is dedicated to musculi (mm.) supraspinatus, infraspinatus, and a small branch to cervical musculature. In F. catus, nervus (n.) medianus receives direct contributions from more ventral rami than P. uncia, possibly reflecting a greater reliance on manual dexterity in prey capture in the former. In addition to primary innervation by n. thoracodorsalis, m. latissimus dorsi is also innervated by n. thoracicus lateralis near the axilla in both taxa, suggesting that it may belong to a complex of proximal forelimb musculature along with mm. pectoralis profundus and cutaneus trunci.

What's suffering got to do with it? A qualitative study of suffering in the context of Medical Assistance in Dying (MAID).

BACKGROUND: Intolerable suffering is a common eligibility requirement for persons requesting assisted death, and although suffering has received philosophic attention for millennia, only recently has it been the focus of empirical inquiry. Robust theoretical knowledge about suffering is critically important as modern healthcare provides persons with different options at end-of-life to relieve suffering. The purpose of this paper is to present findings specific to the understanding and application of suffering in the context of MAID from nurses' perspectives. METHODS: A longitudinal qualitative descriptive study using semi-structured telephone interviews. Inductive analysis was used to construct a thematic account. The study received ethical approval and all participants provided written consent. RESULTS: Fifty nurses and nurse practitioners from across Canada were interviewed. Participants described the suffering of dying and provided insights into the difficulties of treating existential suffering and the iatrogenic suffering patients experienced from long contact with the healthcare system. They shared perceptions of the suffering that leads to a request for MAID that included the unknown of dying, a desire for predictability, and the loss of dignity. Eliciting the suffering story was an essential part of nursing practice. Knowledge of the story allowed participants to find the balance between believing that suffering is whatever the persons says it is, while making sure that the MAID procedure was for the right person, for the right reason, at the right time. Participants perceived that the MAID process itself caused suffering that resulted from the complexity of decision-making, the chances of being deemed ineligible, and the heighted work of the tasks of dying. CONCLUSIONS: Healthcare providers involved in MAID must be critically reflective about the suffering histories they bring to the clinical encounter, particularly iatrogenic suffering. Further, eliciting the suffering stories of persons requesting MAID requires a high degree of skill; those involved in the assessment process must have the time and competency to do this important role well. The nature of suffering that patients and family encounter as they enter the contemplation, assessment, and provision of MAID requires further research to understand it better and develop best practices.

Midline and Mediolateral Episiotomy: Risk Assessment Based on Clinical Anatomy.

Episiotomy is the surgical incision of the vaginal orifice and perineum to ease the passage of an infant's head while crowning during vaginal delivery. Although episiotomy remains one of the most frequently performed surgeries around the world, short- and long-term complications from the procedure are not uncommon. We performed midline and mediolateral episiotomies with the aim of correlating commonly diagnosed postepisiotomy complications with risk of injury to perineal neuromuscular and erectile structures. We performed 61 incisions on 47 female cadavers and dissected around the incision site. Dissections revealed that midline incisions did not bisect any major neuromuscular structures, although they did increase the risk of direct and indirect injury to the subcutaneous portion of the external anal sphincter. Mediolateral incisions posed greater risk of iatrogenic injury to ipsilateral nerve, muscle, erectile, and gland tissues. Clinician discretion is advised when weighing the potential risks to maternal perineal anatomy during vaginal delivery when episiotomy is indicated. If episiotomy is warranted, an understanding of perineal anatomy may benefit diagnosis of postsurgical complications.

Male and female anatomical homologies in the perineum of the dog (Canis familiaris).

Understanding the homologies between male and female perineal structure helps both evolutionary biologists and clinicians better understand the evolution and anatomy of canines. Domestic dogs (Canis familiaris) play an important role in human society, and canine perineal anatomy is important for maintaining dogs' reproductive health for successful breeding and a wide variety of pathologies. Here, we investigate homologies between male and female perineal structure, identifying structures based on common function, anatomical relationships and attachments. In this investigation we dissected 21 male and female large-breed dogs. We find broad structural homologies between male and female dogs related to erection, micturition and defecation, including muscles, fasciae and erectile tissue. Using these homologies will help anatomists and clinicians interpret the anatomical organization of the perineum, a notoriously difficult area of anatomy.

Extraocular muscle architecture in hawks and owls.

OBJECTIVE: A complete and accurate understanding of extraocular muscle function is important to the veterinary care of the avian eye. This is especially true for birds of prey, which rely heavily on vision for survival and yet are prone to ocular injury and disease. To better understand the function of extraocular muscles in birds of prey, we studied extraocular muscle architecture grossly and histologically. ANIMALS STUDIED: This sample was composed of two each of the following species: red-tailed hawk (Buteo jamaicensis), Harris's hawk (Parabuteo unicinctus), great horned owl (Bubo virginianus), and barn owl (Tyto alba). PROCEDURES: All extraocular muscles were dissected and weighed. To analyze muscle fiber architecture, the superior oblique and quadratus muscles were dissected, weighed, and sectioned at 5 µm thickness in the transverse plane. We calculated the physiologic cross-sectional area and the ratio of muscle mass to predicted effective maximum tetanic tension. RESULTS AND CONCLUSIONS: Hawk and owl extraocular muscles exhibit significant physiological differences that play roles in ocular movements and closure of the nictitating membrane. Owls, which do not exhibit extraocular movement, have muscle architecture suited to stabilize the position of a massive, tubular eye that protrudes significantly from the orbit. Hawks, which have a more globose eye that is largely contained within the orbit, do not require as much muscular stability and instead have muscle architecture that facilitates rapid eye movement.

Reorganization of mammalian body wall patterning with cloacal septation.

Septation of the cloaca is a unique mammalian adaptation that required a novel reorganization of the perineum-the caudal portion of the trunk body wall not associated with the hindlimb. Fish, the basal vertebrates, separate ventrolateral body wall musculature of the trunk into two discrete layers, while most tetrapods expand this pattern in the thorax and abdomen into four. Mammals, the only vertebrate group to divide the cloaca into urogenital and anorectal portions, exhibit complex muscle morphology in the perineum. Here we describe how perineal morphology in a broad sample of mammals fits into patterning of trunk musculature as an extension of the four-layer ventrolateral muscular patterning of the thorax and abdomen. We show that each perineal muscle layer has a specific function related to structures formed by cloacal septation. From superficial to deep, there is the subcutaneous layer, which regulates orifice closure, the external layer, which supplements both erectile and micturition function, the internal layer, which provides primary micturition and defecation regulation, and the transversus layer, which provides structural support for pelvic organs. We elucidate how the four-layer body wall pattern, restricted to the non-mammal tetrapod thorax and abdomen, is observed in the mammalian perineum to regulate function of unique perineal structures derived from cloacal septation.

Histological study of white rhinoceros integument.

In this study, we report findings from a microscopic analysis of the white rhinoceros (Ceratotherium simum) integumentary ultrastructure. Skin samples from the cheek, shoulder, flank and rump were taken from a 46-year-old female southern white rhinoceros and examined using H&E and elastic histological stains. The epidermis was thickest in the flank (1.003 mm) followed by the rump, cheek and shoulder. The stratum corneum comprised more than half the epidermal thickness. Numerous melanin granules were found in the basal and spinosum layers. The epidermal-dermal junction was characterized by abundant papillary folds increasing surface contact between integument layers. Most of the dermal thickness consisted of organized collagen bundles with scattered elastic fibers. Collagen fiber bundles were thickest in the flank (210.9 µm) followed by shoulder, rump and cheek. Simple coiled sweat glands were present in the dermis, but hair and sebaceous glands were absent. Together, these data suggest the white rhinoceros has a unique integumentary system among large terrestrial herbivores.

A functional and clinical reinterpretation of human perineal neuromuscular anatomy: Application to sexual function and continence.

Modern anatomical and surgical references illustrate perineal muscles all innervated by branches of the pudendal nerve but still organized into anatomically distinct urogenital and anal triangles with muscles inserting onto a central perineal body. However, these conflict with the anatomy commonly encountered during dissection. We used dissections of 43 human cadavers to characterize the anatomical organization of the human perineum and compare our findings to standard references. We found bulbospongiosus and the superficial portion of the external anal sphincter (EAS) were continuous anatomically with a common innervation in 92.3% of specimens. The superficial transverse perineal muscle inserted anterior and lateral to the midline, interdigitating with bulbospongiosus. The three EAS subdivisions were anatomically discontinuous. Additionally, in 89.2% of our sample the inferior rectal nerve emerged as a branch of S3 and S4 distinct from the pudendal nerve and innervated only the subcutaneous EAS. Branches of the perineal nerve innervated bulbospongiosus and the superficial EAS and nerve to levator ani innervated the deep EAS. In conclusion, we empirically demonstrate important and clinically relevant differences with perineal anatomy commonly described in standard texts. First, independent innervation to the three portions of EAS suggests the potential for functional independence. Second, neuromuscular continuity between bulbospongiosus and superficial EAS suggests the possibility of shared or overlapping function of the urogenital and anal triangles. Clin. Anat. 29:1053-1058, 2016. © 2016 Wiley Periodicals, Inc.

An alternate dissection approach to the female urogenital triangle.

Traditional dissections of the female urogenital (UG) triangle can lead to early destruction of the erectile tissues, associated musculature, and neurovascular structures. Here, we present an alternate dissection of the female UG triangle. Rather than begin the female UG triangle dissection with the fatty tissue of the labia majora, we utilize an early identification of the suspensory ligament of the clitoris to organize the dissection. The suspensory ligament leads to the body of the clitoris, which can be palpated from distal to proximal to find the crura of the clitoris with overlying ischiocavernosus muscles. Once the crura have been defined, the bulbs of the vestibule with overlying bulbospongiosus muscles can be palpated medially and posteriorly. This dissection approach results in a clean dissection that well demonstrates homologies between male and female external genitalia. Through the use of this method, most student dissection attempts are able to demonstrate the erectile tissues and associated musculature that comprise the female UG triangle. This technique can also be used for male UG triangle dissections, encouraging identification of male and female homologies.

A novel method for comparative analysis of retinal specialization traits from topographic maps.

Vertebrates possess different types of retinal specializations that vary in number, size, shape, and position in the retina. This diversity in retinal configuration has been revealed through topographic maps, which show variations in neuron density across the retina. Although topographic maps of about 300 vertebrates are available, there is no method for characterizing retinal traits quantitatively. Our goal is to present a novel method to standardize information on the position of the retinal specializations and changes in retinal ganglion cell (RGC) density across the retina from published topographic maps. We measured the position of the retinal specialization using two Cartesian coordinates and the gradient in cell density by sampling ganglion cell density values along four axes (nasal, temporal, ventral, and dorsal). Using this information, along with the peak and lowest RGC densities, we conducted discriminant function analyses (DFAs) to establish if this method is sensitive to distinguish three common types of retinal specializations (fovea, area, and visual streak). The discrimination ability of the model was higher when considering terrestrial (78%-80% correct classification) and aquatic (77%-86% correct classification) species separately than together. Our method can be used in the future to test specific hypotheses on the differences in retinal morphology between retinal specializations and the association between retinal morphology and behavioral and ecological traits using comparative methods controlling for phylogenetic effects.

Eye shape and the nocturnal bottleneck of mammals.

Most vertebrate groups exhibit eye shapes that vary predictably with activity pattern. Nocturnal vertebrates typically have large corneas relative to eye size as an adaptation for increased visual sensitivity. Conversely, diurnal vertebrates generally demonstrate smaller corneas relative to eye size as an adaptation for increased visual acuity. By contrast, several studies have concluded that many mammals exhibit typical nocturnal eye shapes, regardless of activity pattern. However, a recent study has argued that new statistical methods allow eye shape to accurately predict activity patterns of mammals, including cathemeral species (animals that are equally likely to be awake and active at any time of day or night). Here, we conduct a detailed analysis of eye shape and activity pattern in mammals, using a broad comparative sample of 266 species. We find that the eye shapes of cathemeral mammals completely overlap with nocturnal and diurnal species. Additionally, most diurnal and cathemeral mammals have eye shapes that are most similar to those of nocturnal birds and lizards. The only mammalian clade that diverges from this pattern is anthropoids, which have convergently evolved eye shapes similar to those of diurnal birds and lizards. Our results provide additional evidence for a nocturnal 'bottleneck' in the early evolution of crown mammals.

Comment on "Nocturnality in dinosaurs inferred from scleral ring and orbit morphology".

Schmitz and Motani (Reports, 6 May 2011, p. 705) claimed to definitively reconstruct activity patterns of Mesozoic archosaurs using the anatomy of the orbit and scleral ring. However, we find serious flaws in the data, methods, and interpretations of this study. Accordingly, it is not yet possible to reconstruct the activity patterns of most fossil archosaurs with a high degree of confidence.

Anatomical specializations for nocturnality in a critically endangered parrot, the Kakapo (Strigops habroptilus).

The shift from a diurnal to nocturnal lifestyle in vertebrates is generally associated with either enhanced visual sensitivity or a decreased reliance on vision. Within birds, most studies have focused on differences in the visual system across all birds with respect to nocturnality-diurnality. The critically endangered Kakapo (Strigops habroptilus), a parrot endemic to New Zealand, is an example of a species that has evolved a nocturnal lifestyle in an otherwise diurnal lineage, but nothing is known about its' visual system. Here, we provide a detailed morphological analysis of the orbits, brain, eye, and retina of the Kakapo and comparisons with other birds. Morphometric analyses revealed that the Kakapo's orbits are significantly more convergent than other parrots, suggesting an increased binocular overlap in the visual field. The Kakapo exhibits an eye shape that is consistent with other nocturnal birds, including owls and nightjars, but is also within the range of the diurnal parrots. With respect to the brain, the Kakapo has a significantly smaller optic nerve and tectofugal visual pathway. Specifically, the optic tectum, nucleus rotundus and entopallium were significantly reduced in relative size compared to other parrots. There was no apparent reduction to the thalamofugal visual pathway. Finally, the retinal morphology of the Kakapo is similar to that of both diurnal and nocturnal birds, suggesting a retina that is specialised for a crepuscular niche. Overall, this suggests that the Kakapo has enhanced light sensitivity, poor visual acuity and a larger binocular field than other parrots. We conclude that the Kakapo possesses a visual system unlike that of either strictly nocturnal or diurnal birds and therefore does not adhere to the traditional view of the evolution of nocturnality in birds.

Hawk eyes I: diurnal raptors differ in visual fields and degree of eye movement.

BACKGROUND: Different strategies to search and detect prey may place specific demands on sensory modalities. We studied visual field configuration, degree of eye movement, and orbit orientation in three diurnal raptors belonging to the Accipitridae and Falconidae families. METHODOLOGY/PRINCIPAL FINDINGS: We used an ophthalmoscopic reflex technique and an integrated 3D digitizer system. We found inter-specific variation in visual field configuration and degree of eye movement, but not in orbit orientation. Red-tailed Hawks have relatively small binocular areas (∼33°) and wide blind areas (∼82°), but intermediate degree of eye movement (∼5°), which underscores the importance of lateral vision rather than binocular vision to scan for distant prey in open areas. Cooper's Hawks' have relatively wide binocular fields (∼36°), small blind areas (∼60°), and high degree of eye movement (∼8°), which may increase visual coverage and enhance prey detection in closed habitats. Additionally, we found that Cooper's Hawks can visually inspect the items held in the tip of the bill, which may facilitate food handling. American Kestrels have intermediate-sized binocular and lateral areas that may be used in prey detection at different distances through stereopsis and motion parallax; whereas the low degree eye movement (∼1°) may help stabilize the image when hovering above prey before an attack. CONCLUSIONS: We conclude that: (a) there are between-species differences in visual field configuration in these diurnal raptors; (b) these differences are consistent with prey searching strategies and degree of visual obstruction in the environment (e.g., open and closed habitats); (c) variations in the degree of eye movement between species appear associated with foraging strategies; and (d) the size of the binocular and blind areas in hawks can vary substantially due to eye movements. Inter-specific variation in visual fields and eye movements can influence behavioral strategies to visually search for and track prey while perching.

The nocturnal bottleneck and the evolution of mammalian vision.

Evidence from the early paleontological record of mammalian evolution has often been interpreted as supporting the idea that mammals were nocturnal for most of their early history. Multiple features of extant mammal sensory systems, such as evolutionary modifications to the light-regulated circadian system, photoreceptor complement, and retinal morphology, support this nocturnal hypothesis for mammalian evolution. Here, we synthesize data on eye shape and orbit orientation in mammals as these data compare to other amniotes. Most mammals differ from other amniotes in retaining an eye design optimized for high visual sensitivity, with the requisite reduction in acuity, which is typically restricted to scotopically (i.e. low light) adapted amniotes. Mammals also possess the more convergent (similarly facing) orbits and, on average, the largest binocular visual fields among amniotes. Based on our analyses, we propose that extant mammals retain a scotopic eye design as well as expanded binocular zones as a result of their nocturnal origin. Only anthropoid primates notably differ from general mammalian patterns, and possibly have evolved an eye shape more typical of the ancestral amniote condition.

Optic foramen morphology and activity pattern in birds.

The optic nerve is the sole output of visual information from the ganglion cell layer of the retina to the brain in vertebrates. The size of the optic nerve is predicted to be closely associated with activity pattern, and, in many birds, the size of the optic foramen approximates the size of the optic nerve. Specifically, nocturnal species should have relatively smaller optic foramina than diurnal species because of differences in retinal pooling between activity patterns. If optic foramen morphology varies predictably with activity pattern in birds, this variable may be useful for interpreting activity pattern for birds that do not have soft tissue available for study, specifically for fossils. Across 177 families (from 27 orders), we describe four different optic foramen morphologies, only one of which corresponds well with the size of the optic nerve and is therefore appropriate for activity pattern analyses. Here, we test our hypothesis that nocturnal species will have relatively smaller optic foramina than diurnal species, across all species that we measured that have a discrete optic foramen. Regression analyses using species as independent data points and using comparative methods yielded significant differences in optic foramen size between nocturnal and diurnal species relative to three variables: head length, orbit depth, and sclerotic ring inner diameter. Nocturnal species consistently exhibit significantly smaller relative optic foramen diameters than diurnal species. Our results indicate that optic foramen diameter, in combination with either the sclerotic ring or the orbit diameter, can be used to predict activity pattern.

The relationship between the lizard eye and associated bony features: a cautionary note for interpreting fossil activity patterns.

Activity pattern, the time of day when an animal is active, is associated with ecology. There are two major activity patterns: diurnal (awake during the day in a photopic environment) and nocturnal (awake at night in a scotopic environment). Lizards exhibit characteristic eye shapes associated with activity pattern, with scotopic-adapted lizard eyes optimized for visual sensitivity with large corneal diameters relative to their eye axial lengths, and photopic-adapted lizards optimized for visual acuity, with larger axial lengths of the eye relative to their corneal diameters. This study: (1) quantifies the relationship between the lizard eye and its associated bony anatomy (the orbit, sclerotic ring, and associated skull widths); (2) investigates how activity pattern is reflected in that bony anatomy; and (3) determines if it is possible to reliably interpret activity pattern for a lizard that does not have the soft tissue available for study, specifically, for a fossil. Knowledge of extinct lizards' activity patterns would be useful in making paleoecological interpretations. Here, 96 scotopic- and photopic-adapted lizard species are analyzed in a phylogenetic context. Although there is a close relationship between the lepidosaur eye and associated bony anatomy, based on these data activity pattern cannot be reliably interpreted for bony-only specimens, such as a fossil, possibly because of the limited ossification of the lepidosaur skull. Caution should be exercised when utilizing lizard bony anatomy to interpret light-level adaptation, either for a fossil lizard or as part of an extant phylogenetic bracket to interpret other extinct animals with sclerotic rings, such as dinosaurs.

The anatomical relationships between the avian eye, orbit and sclerotic ring: implications for inferring activity patterns in extinct birds.

Activity pattern, or the time of day when an animal is awake and active, is highly associated with that animal's ecology. There are two principal activity patterns: diurnal, or awake during the day in a photopic, or high light level, environment; and nocturnal, awake at night in scotopic, or low light level, conditions. Nocturnal and diurnal birds exhibit characteristic eye shapes associated with their activity pattern, with nocturnal bird eyes optimized for visual sensitivity with large corneal diameters relative to their eye axial lengths, and diurnal birds optimized for visual acuity, with larger axial lengths of the eye relative to their corneal diameters. The current study had three aims: (1) to quantify the nature of the relationship between the avian eye and its associated bony anatomy, the orbit and the sclerotic ring; (2) to investigate how activity pattern is reflected in that bony anatomy; and (3) to identify how much bony anatomy is required to interpret activity pattern reliably for a bird that does not have the soft tissue available for study, specifically, for a fossil. Knowledge of extinct avian activity patterns would be useful in making palaeoecological interpretations. Here eye, orbit and sclerotic ring morphologies of 140 nocturnal and diurnal bird species are analysed in a phylogenetic context. Although there is a close relationship between the avian eye and orbit, activity pattern can only be reliably interpreted for bony-only specimens, such as a fossil, that include both measurements of the sclerotic ring and orbit depth. Any missing data render the fossil analysis inaccurate, including fossil specimens that are flat and therefore do not have an orbit depth available. For example, activity pattern cannot be determined with confidence for Archaeopteryx lithographica, which has a complete sclerotic ring but no orbit depth measurement. Many of the bird fossils currently available that retain a good sclerotic ring tend to be flat specimens, while three-dimensionally preserved bird fossils tend not to have a well-preserved sclerotic ring or a well-defined optic foramen, necessary for delimiting the orbit depth.

Comparative analysis of the size and shape of the lizard eye.

Lizards occupy both scotopic (light-limited) and photopic (light-rich) environments, thereby making this clade ideal for analyses of eye morphology adaptations. This study examines how in lizards the morphology of the eye varies according to activity in these different light environments. Measurements were collected on corneal diameters and axial lengths of the eye for 239 specimens of 116 lizard species (including Sphenodon) that include both species with scotopic and photopic visual adaptations. I show that the light level available to a lizard for vision has a significant effect on eye shape and size. Scotopic lizards have eye shapes that are optimized for visual sensitivity, with larger corneal diameters relative to axial lengths. However, photopic lizards do not exhibit absolutely larger axial lengths than do scotopic lizards, and the groups have the same absolute axial lengths of the eye. Results also indicate that the light level the lizard functions under is a more significant influence on eye shape, as defined by the relationship between corneal diameter and axial length of the eye, than is phylogeny.