Morphology of the pattern of branching of the aortic arch (Arcus aortae) in Syrian hamsters (Mesocricetus auratus).

The branching patterns of the aortic arches of 28 adult male and female Syrian hamsters (SH) were thoroughly examined under a stereomicroscope for the first time by using latex injection and corrosion casting to determine their general arrangements and morphological variations as well as their differences and similarities to other rodents and rabbits. Three major arteries, namely, the brachiocephalic trunk (BC), left common carotid artery (CC) and left subclavian artery (SA), originating from the aortic arch (AR), were uniformly noted in SH. The BC was consistently divided into the right SA and the right CA. SA in SH normally releases the internal thoracic, deep cervical, dorsal scapular, vertebral, superficial cervical and supreme intercostal arteries. The costocervical trunk typically consisted of supreme intercostal and internal thoracic arteries and a common trunk for dorsal scapular and deep cervical arteries. To comprehend the comparative morphology of the pattern of branching of AR more completely, our results were compared with previous studies in rodents and rabbits. (1) The general morphology of the great arteries from AR in SH was similar to that in mole rats, rats, mice, porcupines, and gerbils but was essentially different from that in rabbits, guinea pigs, red squirrels, ground squirrels, pacas and chinchillas. (2) The typical pattern of the branching of the subclavian arteries in SH was similar to that in guinea pigs, rats, and rabbits but was different from that of the reported rodents regardless of the origins of the bronchoesophageal and internal thoracic arteries and the composition of the costocervical trunk.

Anatomical study of arterial arrangement of the spinal cord in Syrian hamsters (Mesocricetus auratus).

This study aimed to investigate the arterial arrangement of the spinal cord in Syrian hamsters, and to identify differences and similarities to humans and experimental animals that are mostly used as models in studies into ischemic spinal cord injuries. This observational anatomical study was conducted on 20 adult Syrian hamsters using dissection and corrosion casting technique. The general anatomy of the arterial blood supply of spinal cord was obtained and noted as follows: (1) high variability in the level of the origin of right and left vertebral arteries, (2) the independent origin of dorsal intercostal arteries, (3) origin of lumbar arteries as a common trunk with right and left divisions, (4) presence of dorsal and ventral radicular branches in both sides of the cervical spinal cord with almost the same frequency, (5) greater presence of ventral and dorsal radicular branches in the left side of the thoracolumbar spinal cord, (6) two dorsal spinal arteries originating from the posterior inferior cerebellar arteries and extending to the caudal end of the thoracic spinal cord, (7) continuous ventral spinal artery originating from both vertebral arteries and extending to the conus medularis, and (8) presence of the artery of Adamkiewicz in the thoracic region of the spinal cord. From comparative anatomy viewpoints, the arteries supplying the spinal cord of Syrian hamsters exhibit many similarities with humans, laboratory rodents, and rabbits in many aspects compared to dogs, cats, and pigs. Overall, Syrian hamsters can be used as a proposed model in experimental studies of the spinal cord ischemia.

Morphotopographic characteristics of the extrinsic innervation of the heart in guinea pigs (Cavia porcellus).

BACKGROUND: No reports have been made on the entire extrinsic innervation of the heart in small laboratory animals. Therefore, this study examined the detailed morphotopographic features of the extrinsic cardiac autonomic nervous system (ECANS) with its adjacent structures (1) to record the general morpho-topography and variations of the ECANS in guinea pigs, (2) to compare it with previous reports on common laboratory rodents (rats, mice, and Syrian hamsters), rabbits, domesticated animals (cats, dogs, sheep, goats, oxen, pigs, and horses), primates, and humans, and (3) to infer the macroscopic evolutionary changes they presented. METHODS: The sympathetic ganglia, vagi, and emitting cardiac nerves/branches in the cervical and thoracic regions were dissected in 24 sides of 12 formalin-fixed, arterially injected adult male and female guinea pigs under a stereomicroscope. RESULTS: The ECANS in guinea pigs presented following general morphologic characteristics: (1) constant existence of the cranial cervical ganglion (CG) and placing caudal to the cranial base over the ventrolateral aspect of the longus capitis muscle, dorsomedial to the common carotid artery and communicating to the first two cervical spinal nerves, (2) the lack of the vago-sympathetic trunk, (3) the existence of the middle cervical ganglion (MG) and lying on the lateral aspect of the longus colli muscle (LC) at the level of the seventh cervical vertebra, (4) constant existence of the cervicothoracic ganglion (CT) composing generally from the caudal cervical ganglion and 1-3 thoracic ganglia and placing ventral to the first and second intercostal spaces over the lateral aspect of the LC and communicating to the eight cervical and first three thoracic spinal nerves in addition to the vertebral nerve, (5) constant existence of the limbs of the ansa subclavia (AS) joining the CT to MG, (6) the existence of individual thoracic ganglia from the 4th to the 12th and joining by single interganglionic branches (IGBs), and communicating to corresponding thoracic nerve, (7) the intimate relation between the caudal part of the thoracic sympathetic chain and the quadratus lumborum muscle, (8) the main cardiac nerves (CNs) emerging from the CT, (9) the lack of CNs springing generally from the CG, ST, AS, MG, or individual thoracic ganglia or their IGBs, and (10) the existence of the cardiac branches (CBs) emerging from the vagi and recurrent laryngeal nerves. The ECANS morphology in guinea pigs also shows sex and laterality differences. CONCLUSIONS: The general anatomical arrangement of the sympathetic components of the ECANS in guinea pigs extremely displaced features common to rats and Syrian hamsters regardless of the existence of MG and the close relation between the thoracic sympathetic chain and the quadratus lumborum muscle. However, the position and organization of the CT, along with its rami communicantes to spinal nerves in guinea pigs quite resembled those seen in rats. The general macroscopic arrangement of the sympathetic components of the ECANS in guinea pigs resembled that seen in rabbits regardless of the organization and location of the CT. The general morphology of the sympathetic components of the ECANS demonstrated markedly morphological variations and similarities among common laboratory rodents, rabbits, domesticated animals (DNs), primates, and humans. The main variations consisted of the position of the CG and its rami communicantes with the spinal nerves, the relation between the vagi and sympathetic trunks in the neck, the existence of the MG, the location and arrangement of the CT, the origins and incidences of the cardiac nerves, and the main sympathetic contributors. The general macroscopic architecture of the parasympathetic components of the ECANS in guinea pigs quite resembled that seen in domesticated animals, primates, and humans. Evolutionary comparative morphologic characteristics of the ECANS are discussed in detail and evolutionary differences and similarities of the ECANS have been found from common laboratory rodents, rabbits, domesticated animals, and primates to humans.

Detailed gross anatomy and topography of the sympathetic cardiac nerves and related ganglia in Syrian hamsters (Mesocricetus auratus).

BACKGROUND: The detailed morphology and topography of the sympathetic cardiac nerves (SCNs) and ganglia with their surrounding structures in Syrian hamsters were examined to document the general topography and morphology and variations and to discuss the comparative anatomy between the SCNs and ganglia in Syrian hamsters and other rodents, as well as their comparative morphology and macroscopic evolutionary changes among rodents, rabbits, domestic animals (cats, dogs, sheep, goats, oxen, pigs and horses), primates, and humans. METHODS: The composition of the cervical and thoracic parts of the sympathetic trunks and ganglia was bilaterally microdissected in twenty-eight sides of 14 adult male and female Syrian hamsters under a stereomicroscope. RESULTS: The general morphology of the SCNs and related ganglia in Syrian hamsters was obtained and noted as follows: (1) the absence of the vago-sympathetic trunk, (2) the absence of the middle cervical ganglion (MG), (3) constant presence of the cervicothoracic ganglion (CT) comprising generally from the caudal cervical ganglion and 1-2 thoracic ganglia and locating over the lateral surface of the longus colli muscle ventral to the heads of the first two ribs and communicating to the eight cervical and first two thoracic spinal nerves (C8-T2) in addition to the vertebral nerve, (4) extensive coverage of the lateral surface of the CT by branches of the subclavian artery, (5) the cranial and caudal limbs of the ansa subclavia (AS) joining the CT to the caudal end of the cervical sympathetic trunk, (6) the presence of an independent thoracic ganglion from the 2nd or 3rd to the 13th and connecting by single interganglionic branches, and communicating to each thoracic spinal nerve, (7) close relationship between the caudal portion of the thoracic sympathetic trunk and the psoas minor muscle, (8) the primary cardiac nerves (CNs) arising from the CT, and (9) the absence of CNs originating generally from the cervical sympathetic trunk, AS, MG, or independent thoracic ganglia or their interganglionic branches. Individual variations of the SCNs and ganglia in Syrian hamsters were noted, including the absence of the ansa subclavia on 5/28 sides (17.86%), the presence of the intermediate ganglia (IG) placed on the C7 on 3/28 sides (10.71%) or the C8 on 3/28 sides (10.71%), and no CNs arising from the IG as well as the presence of the double thoracic sympathetic trunk on 5/28 sides (17.86%). The anatomical characteristics of the SCNs and related ganglia were also exhibited sex and laterality differences. CONCLUSIONS: From a comparative anatomy viewpoint, the general morphology of the SCNs and related ganglia in Syrian hamsters was very similar to that in rats but was considerably different from that in guinea pigs, especially concerning the MG, cranial position and composition of the CT. The general morphology of the SCNs and related ganglia in Syrian hamsters and other laboratory rodents resembled that of rabbits but was essentially different from that in rabbits with respect to the cranial position and composition of the CT. The general morphology of the SCNs and ganglia exhibited significant morphological differences and similarities among laboratory rodents, rabbits, domestic animals, primates, and humans. The main differences include the relationship between the cervical parts of the vagus nerve and sympathetic trunk, the presence of the MG, the position and composition of the CT, the origins and frequencies of the cardiac nerves, and the primary sympathetic contributor. From macroscopic evolutionary change, the expansion of the range of the SCNs origin has occurred from laboratory rodents, rabbits, domestic animals, and primates to humans.

Detailed gross anatomic and sialographic characteristics of major salivary glands in water buffaloes (Bubalus bubalis).

To clarify the detailed general architecture and topography of major salivary glands and demonstrate a fine anatomy of the ductal system of the glands in water buffaloes, we conducted gross anatomic and sialographic investigations of glands in 14 half heads from seven water buffaloes. The position of the mandibular gland, course of mandibular duct relative to monostomatic gland, a rostral extension of polystomatic gland, and site of origin of monostomatic duct in buffaloes essentially differed from those of various ruminants. The shape of the parotid and mandibular glands, and origin of their ducts, lacking filling of retromandibular fossa by parotid gland, the topography of mandibular gland relative to the parotid gland and mandibular lymph node, caudal extension of polystomatic gland, rostral extension of monostomatic gland, and location of polystomatic gland relative to monostomatic gland in buffaloes were very similar to those in ox. However, several considerable differences in morphology of glands in buffaloes and ox were recognized. Major salivary glands in buffaloes almost show 'grazing ruminants' morphological and morphometrical characteristics. Within parotid, mandibular, and monostomatic glands in buffaloes, there was a ductal arborization pattern in lateral sialograms. Whereas the main parotid duct was formed by a union of two central branches of the intraglandular duct, main mandibular, and monostomatic ducts were consisted of one central branch. The pattern of peripheral branches from the central branch of intraglandular duct in buffaloes was significantly different among the glands. Our detailed sialography of ductal morphology and morphometry can be helpful in accurate diagnosis of gland diseases in live water buffaloes.

Developmental Morphology and Topography of the Components of the Cervical Sympathetic Trunk in Sheep (Ovis aries) During the Fetal Period.

The objective of this study was to clarify the typical architecture and morphological variations of cervical sympathetic trunk (CST) in sheep during fetal period. Components of CST were examined on both sides of 40 male and female sheep fetuses aged from 60 to 140 days under a stereomicroscope. Skeletotopy and frequency of presence of cranial cervical ganglion (CCG), syntopy of cervical ganglia, and composition and topography of vagosympathetic trunk were consistent among specimens whereas the shape of cervical ganglia, the skeletotopy and number of three middle cervical ganglia (MG), and the frequency of communicating branches of CCG to the first cervical spinal nerve exhibited differences during fetal period. A reduction in the number of MG and the caudal movement of main MG were noted by increasing fetal age. Based on these detailed findings, comparative and developmental anatomy and evolutionary changes are discussed and compared with previous studies. The number of MG, skeletotopy of CCG and main MG, the number and range of communicating branches of CCG to spinal nerves, and the association of vagus and sympathetic nerves in fetal sheep were fundamentally different from those of mostly reported species. These results suggest that data obtained from CST of fetal sheep are significantly different from those obtained from humans, and it is problematic to apply them to humans because of the more cranial position of CCG, very narrow contribution of CCG to spinal nerve, absence of the vertebral ganglion, existence of multiple MG, and no communicating branches from MG to spinal nerves. Anat Rec, 300:2250-2262, 2017. © 2017 Wiley Periodicals, Inc.

Morphometric development of the vertebral segments of the vertebral column in the goat (Capra hircus) during the fetal period / Desarrollo morfométrico de los segmentos vertebrales de la columna vertebral en cabra (Capra hircus) durante el periodo fetal

Understanding normal fetal growth rates of the vertebral column, and between species, provide a basis to establish reference values for evaluation of body development and estimation of fetal age by ultrasonography. Goats are also widely used in biomedical perinatal research and are still considered a key to understanding the skeletal development. This study was carried out to clarify growth of length of vertebral column at segmental, regional, and total level of vertebral column in the fetal goats during different gestational age. The length of each vertebral segment of 25 goat fetuses, aged between 6 and 20 weeks were measured for each vertebra using a digital caliper. Our study demonstrated differences among various fetal ages in terms of regional, segmental, and total growth rate of the length of vertebral segments. With increase of fetal age, the relative length of vertebral segments of cervical, thoracic and lumbar regions diminished, whereas sacral and caudal regions increased in relative length. The thoracic vertebrae were the longest followed by cervical, lumbar, caudal, and sacral regions except at the oldest fetuses where caudal region became longer than lumbar region. Although the longest and shortest vertebral segments in cervical and lumbar regions were consistent among age groups, the trend of segmental growth of the vertebral regions was variable. Based on these detailed findings, the relative regional lengths of vertebral column were essentially different among fetal goats, humans, and neonatal rats. There is also a general trend of increasing segmental and regional initial growth and there is a relatively significant increase in growth rate caudally along the column during fetal period. This research yield important results that may be also useful for future orthopedic studies that contemplate the use of goat as a new model for the human spine.

Entender el crecimiento fetal normal de la columna vertebral entre las especies, proporciona una base para establecer valores de referencia en la evaluación del desarrollo corporal y la estimación de la edad fetal por ultrasonografía. Las cabras se utilizan frecuentemente en investigaciones biomédicas perinatales y son consideradas clave en el estudio del desarrollo esquelético. Este estudio se realizó con el objetivo de determiner el crecimiento de longitud de la columna vertebral a nivel segmentario, regional y total de la columna vertebral en cabras fetales durante diferentes etapas gestacionales. La longitud de cada segmento vertebral de 25 fetos de cabra, con edades comprendidas entre las 6 y 20 semanas se midió utilizando un calibre digital. Nuestro estudio demostró diferencias entre varias edades fetales en términos de tasa de crecimiento regional, segmentario y total de longitud de los segmentos vertebrales Con el aumento de la edad fetal, la longitud relativa de los segmentos vertebrales de las regiones cervical, torácica y lumbar disminuyó, mientras que las regiones sacras y caudales aumentaron en longitud relativa. Las vértebras torácicas fueron las más largas seguidas por las regiones cervical, lumbar, caudal y sacral excepto en los fetos más antiguos donde la región caudal se hizo más larga que la región lumbar. Aunque los segmentos vertebrales más largos y más cortos en las regiones cervical y lumbar fueron consistentes entre los grupos de edad, la tendencia de crecimiento segmentario de las regiones vertebrales fue variable. En base a estos resultados, las longitudes relativas de columna vertebral fueron esencialmente diferentes entre cabras fetales, humanos y ratas neonatas. También existe una tendencia general de aumento del crecimiento inicial segmentario y regional, como tambien un aumento relativamente significativo en la tasa de crecimiento a lo largo de la columna durante el período fetal. Esta investigación arroja importantes resultados que también pueden ser útiles para futuros estudios ortopédicos que contemplan el uso de la cabra como un nuevo modelo para la columna vertebral humana.

Immunohistochemical characteristics of neurons in the ganglia of the greater splanchnic nerve of the pig.

INTRODUCTION: Greater splanchnic nerve (GSN) is by far the largest of the splanchnic nerves and connects the paravertebral and prevertebral ganglia to transmit the majority of nociceptive information from the viscera. Despite its importance, the immunohistochemical features of the porcine GSN neurons have not yet been examined. Therefore, the aim of the study was to investigate the neurochemistry of the porcine GSN neurons and to compare their neurochemical coding with those of the paravertebral and prevertebral ganglia. MATERIAL AND METHODS: Four gilts of Large White Polish breed were examined in this study. Antibodies to tyrosine hydroxylase (TH), dopamine b-hydroxylase (DBH), choline acetyltransferase (ChAT), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), somatostatin (SOM), galanin (GAL), methionine-enkephalin (MET), calcitonin gene-related peptide (CGRP), and substance P (SP) were used for immunohistochemical detection of classical neurotransmitters marker enzymes and neuropeptides in neuronal cell bodies of the GSN. RESULTS: Double-labeling immunofluorescence revealed that virtually all GSN neurons exhibited the presence of catecholamine-synthesizing enzymes (TH/DBH-positive) and subpopulations of neurons contained immunoreactivity to NPY, VIP, SOM, GAL and MET. However, CGRP and SP-immunoreactivity were not observed in neuronal somata. CONCLUSIONS: Our data strongly suggest that the general immunohistochemical characterization of ganglion cells in the porcine greater splanchnic nerve is similar to that of the prevertebral ganglia (e.g. celiacomesenteric ganglion).

Topography and morphology of the bovine cranial cervical ganglion and its branches / Topografía y morfología del ganglio cervical craneal bovino y sus ramos

A detailed submacroscopic anatomical study of the cranial cervical ganglion (CCG) and its branches with its adjoining structures was carried out by examining 14 halves of seven heads of Holstein cattle under a magnifying lens to provide comprehensive descriptions with color photographs of the location, relation to neighboring structures, morphometry, and morphology of CCG and its branches. Our results were compared with previously nerves including jugular nerve; internal and external carotid nerves extremely, obtained morphological data on CCG in other ungulates to clarify the detailed comparative anatomy of CCG among them. The morphology of CCG and its branches in bovine was significantly and tangibly different from that of in other reported ungulates, especially in the direction of the ventral and dorsal poles of CCG being caudodorsal and rostroventral respectively, being larger and slightly more rostral, covered laterally by the dorsal part of the stylohyoid bone and caudal stylopharyngeus muscle, close relation of CCG to the medial retropharyngeal lymph node, wider distributions of external carotid nerve and its plexus to the adjacent arteries and visceral structures, lacking a communicating branch with the cervical spinal nerve, although all typical branches including the jugular nerve, carotid sinus branch, internal and external carotid nerves, communicating branches to vagus, glossopharyngeal, hypoglossal, cranial laryngeal, pharyngeal branch of vagus nerves, and close relationship between CCG and the longus capitis muscle, vagus nerve, and internal carotid artery were almost consistently present among the ungulates. The site of origin and the number of the major nerves including jugular nerve, internal and external carotid nerves extremely differed among the ungulates.

Se realizó un estudio anatómico submi-croscópico detallado del ganglio cervical craneal (GCC) y sus ramos, con las estructuras adyacentes, mediante el examen de 14 hemicabezas, correspondientes a siete cabezas de ganado Holstein, bajo aumento, para proporcionar descripciones completas; además se tomaron fotografías a color de la ubicación, su relación con estructuras vecinas y la morfometría y morfología del GCC y sus ramos. Se compararon los resultados obtenidos relacionados con los nervios, incluyendo las arterias carótidas interna y externa; los datos morfológicos obtenidos del GCC de otros ungulados tal vez aclaren la anatomía comparativa detallada del GCC entre los ungulados. Encontramos diferencia significativas en la morfología del GCC y sus ramos en comparación con otros ungulados reportados en la literatura, particularmente en la dirección de los polos ventral y dorsal del GCC, siendo estos caudodorsal y rostroventral respectivamente, presentándose más grande y ligeramente más rostral, cubierto lateralmente por la parte dorsal del hueso estilohioídeo y el músculo estilofaríngeo caudal. Se evidenció una estrecha relación del GCC con los nodos linfáticos retrofaríngeos mediales, con distribuciones más amplias del nervio carotídeo interno y el plexo adyacente a las arterias y estructuras viscerales, careciendo de un ramo comunicante con el nervio espinal cervical. En todos los ungulados se encontraron consistentemente todos los ramos nerviosos típicos, incluyendo el nervio yugular, el ramo del seno carotídeo, los nervios carotídeos interno y externos, los ramos comunicantes para el nervio vago, glosofaríngeo, hipogloso, laringeo craneal, ramo faríngea del nervio vago, y la estrecha relación entre el GCC y el músculo largo de la cabeza, el nervio vago y la arteria carótida interna. Se determinaron diferencias importantes en el sitio y origen de la mayoría de los nervios, incluyendo el nervio yugular y los nervios carotídeos interno y externos.

Detailed Anatomy of the Cranial Cervical Ganglion in the Dromedary Camel (Camelus dromedarius).

The detailed morphology and topography of the cranial cervical ganglion (CCG) with its surrounding structures were studied in 10 sides of five heads of adult one-humped camel to determine its general arrangement as well as its differences and similarities to other animals. The following detailed descriptions were obtained: (1) the bilateral CCG was constantly present caudal to cranial base at the rostroventral border of the occipital condyle over the caudolateral part of nasopharynx; (2) the CCG was always in close relations medially with the longus capitis muscle, rostrolaterally with the internal carotid artery, and caudally with the vagus nerve; and (3) the branches of the CCG were the internal carotid and external carotid nerves, jugular nerve, cervical interganglionic branch, laryngopharyngeal branch, carotid sinus branch and communicating branches to the vagus, and first spinal nerves. In conclusion, there was no variation regarding topography of dromedary CCG among the specimens, in spite of typical variations in number, and mainly in origin of nerve branches ramifying from the CCG. In comparative anatomy aspect, the close constant relations, and presence of major nerves (internal/external carotid and jugular nerves) of dromedary CCG exhibited a typical reported animal's pattern. However, the shape, structures lateral to the CCG, the origin and course pattern of external carotid and jugular nerves, the number of the major nerves branches, the communicating branches of the CCG to the spinal and cranial nerves, and the separation of most rostral parts of vagosympathetic trunk of dromedary were different from those of most reported animals.

Metrical analysis of dromedary digital bones.

Dromedary camels are large even-toed ungulates which are well adapted to life in large deserts. Examinations of their feet have revealed many structural peculiarities. We have measured the digital bones of the dromedary in order to determine whether there are morphometric variations in the digital bones between the lateral and medial sides in individual limbs and/or in the right and left thoracic and pelvic limbs, with the aim to clarify whether there are anatomical differences in the digital bones of dromedary as a suborder of the order Artiodactyla. Measurements were made of 240 lateral and medial proximal, middle, and distal phalanges in the left and right thoracic and pelvic limbs of ten healthy adult male dromedaries, ranging in age from 6 to 10 years. A total of 17 linear dimensions were measured using a caliper. The results indicate that there are no significant differences between corresponding measurements of digital bones of the lateral and medial in the same limb, nor between measurements of the right and left sides. The lengths and widths of the proximal and middle, and distal phalanges in the thoracic limb were found to be greater than those of the pelvic limb. The sum of the total lengths of the three phalanges of the thoracic limbs was 15 mm greater than that of the phalanges of the pelvic limbs due to a longer proximal phalanx (76 %) and middle phalanx of the former (24 %). The perspectives obtained by our morphometric study of dromedary digital bones not only provide a tool to distinguish the osteological remains of the dromedary from those of the Bactrian camel or other artiodactyls in archaeological sites, but they also suggest a possible influence of digital structure on digit functions and digital disorders.

A case of conjoined twins (thoraco-omphalopygopagus tribrachius tetrapus) in lamb.

Nearly completed conjoined or fused symmetrical twins are generally called diplopagus. Sheep conjoined twins have been reported less than cow. An apparently female conjoined twin lambs was examined based on external and internal features. In radiology, two vertebral columns and two pairs of the ribs were seen. Only two heads and two necks were separated (thoraco-omphalopygopagus). There were three forelimbs (tribrachius), one of which grew on dorsal region as a notomelus. Teat buds of the monsters differed in number. Only one lamb had umbilicus, including one umbilical vein, and two umbilical arteries locating besides one urinary bladder. This lamb had also one uterus. Two-separated alimentary tracts were observed in a common abdomen. Common thorax and abdominal cavities were separated by a diaphragm. There were two esophageal hiatuses, and two caval foramina but only one aortic hiatus. Two pairs of lungs and two unequal and connected hearts in a common pericardium were observed. Abnormality of the circulatory system might have caused the death of the twins.

Prenatal development of the fetal thoracic sympathetic trunk in sheep (Ovis aries).

This study aims at clarifying the detailed morphological and topographical changes of the thoracic part of the sympathetic trunk of sheep during fetal development. Bilateral micro-dissection of the thoracic sympathetic trunk was performed on 40 sheep fetuses aged 6-20 weeks (18 males and 22 females) under a stereomicroscope. The cervicothoracic ganglion (CTG) was observed on 75/80 sides (93.7%) and was composed of the caudal cervical and the first thoracic ganglia on 45/80 sides (56.2%), and of the caudal cervical and the first two thoracic ganglia on 30/80 sides (37.5%). The presence of the two last (12th-13th) thoracic ganglia was not constant. The influence of the sex, the side of the body, and the ages of the fetus on the morphology and topography of the thoracic sympathetic trunk in sheep were identified. In spite of the differences in the morphology and topography of the thoracic sympathetic trunk between early and late fetal developments, the morphology and topography of the older fetal thoracic sympathetic trunk tended to be similar to that of the adult sheep. To comprehend the comparative morphology of the fetal thoracic sympathetic trunk more completely, our results were compared with previous studies. Consequently, differences and similarities in the composition and position of the CTG, presence of single caudal cervical ganglion without fusion to the thoracic ganglia, and absence of the thoracic ganglia, and presence of splitting of the interganglionic branch were found among sheep, pig, and human fetuses. Therefore, sheep might be the appropriate animal model to be applied in human sympathetic nervous system.