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ThesisItem Open Access COMPUTED RADIOGRAPHIC STUDIES ON SIZE OF THE HEART BASED ON VERTEBRAL HEART SCORE IN DOGS AT DIFFERENT AGE GROUPS(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517502. (A.P.) INDIA, 2018-12) SWETHA, PANDIKUNTA; KISHORE, P. V.S.(MAJOR); NAGAMALLESWARI, Y; RAGHUNATH, MThe present study was conducted on 54 clinically healthy dogs of either sex without any cardiac and pulmonary abnormalities. Computed thoracic radiographs available from the recorded data were studied to determine the VHS values in different skull types with one breed as representative sample in each type viz. Brachycephalic (Pug), Mesaticephalic (Labrador retriever) and Dolichocephalic (German shepherd). Dogs in each breed were divided into three age groups viz. group-I (< 6 months), group-II (7-12 months) and group III (>12 months). In Pugs, the gross anatomical size of the heart increased from the age of 6 months to >12 months on left lateral, right lateral and dorsoventral views (p<0.01). There was no significant increase in the gross anatomical size of the heart on manually measured left lateral and right lateral views. Higher VHS values were observed on the right lateral projection than on left lateral projection in both CR and manual methods in all the age groups of all the three breeds. VHS values were not influenced by the age in all the three age groups. There was no significant increase in the gross anatomical size of the heart on left lateral, right lateral and dorsoventral views both by CR and manual measurement. In a comparison of CR and manual methods, the manual VHS values were higher compared to the CR values in both lateral views in Pugs and German shepherd dogs. In Labrador retrievers, the CR VHS values were higher compared to the manual values in both lateral views. There was no significant increase in the gross anatomical size of the heart among the three age groups in the Labrador retrievers and German shepherds. There was no significant variation in the gross anatomical size of the heart up to 12 months of age and at more than 12 months of age the size of the heart was increased markedly in Pugs. In all age groups, the VHS values were highest in Pugs followed by Labrador retrievers and German shepherds, indicating that the size of the heart was larger in Pugs followed by Labrador retrievers and German shepherds. There was no correlation between the body weight and the VHS values among all the three age groups in all the three breeds. In addition to the variations among the three age groups within each breed, variations among the three breeds within the same age group were also found. Group-I showed no variation in all views. Group-II showed no variation on LL, RL and DV views. Group-III showed no variation only in DV view. All haematological and serum biochemical values calculated were within the normal reference range indicating the normal health status of the dogs.ThesisItem Open Access OTOGENESIS IN THE FETUS OF SHEEP (Ovis aries)(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517502. (A.P.) INDIA, 2018-10) KARUNA SRI, VADDI; NAGAMALLESWARI, YAMANI(MAJOR); RAJU, N.K.B.; SREENU, MAKKENA; RAMANI PUSHPA, R.N.The present study was undertaken to elucidate the developmental changes in ear. The study was conducted on 60 embryos and fetuses of Nellore sheep between 22 to 145 gestational days. Morphogenesis revealed that five aural hillocks appeared at 23 days fused to form the pinna later. External acoustic meatus (EAM) appeared first at 24 days. Hairs were apparent on EAM by 126 days. Pinna was pendulous and elongated at 145 days. Tympanic cavity presented three tiny ossicles malleus, incus and stapes at the epitympanic region by 63 days. Rostral process of malleus and Lenticular bone were absent in sheep. The ossified part of tympanic ring appeared in semi lunar shape by 55 days. Ossification initiated in vestibule and cochlea by 70 days. Histogenesis revealed small cone shaped pinna at 24 days. Pharyngeal cleft modified into EAM by 39 days and canalized by 49 days. Epithelium of pinna was keratinized at 99 days. The meatal plug appeared first in 24 day embryos and formed primary external auditory canal (EAC) between 31 to 39 days. The ceruminous and sebaceous glands were first identified by 80 days. Middle fibrous layer of ear drum was formed at 126 days. Tympanic membrane appeared trilaminar and EAC was completely canalized by 140 days. Meckel’s and Reichert’s cartilages developed as mesenchymal condensation by 23 days. The distal part of Meckel’s cartilage modified into malleus and incus. Blastemal cells of Reichert’s cartilage modified as stapes. Tubo tympanic recess (TTR) differentiated between 24 to 27 days. Ossification initiated in malleus, incus and stapes at 63, 78 and 80 days respectively. Incudo-malleal and incudo-stapedial joints were established as diarthrodial joints by 80 and 85 days respectively. Eustachian tube lined by psedostratified ciliated columnar epithelium and Meckel’s cartilage disappeared by 85 days. Ossicular ligaments were differentiated at 104 days. The tympanic cavity comprised of fully grown ossified ossicles as adult by 140 days. Otic placode of inner ear differentiated into the otocyst and acoustico-facial ganglion was formed from otocyst by 22 days. Otocyst underwent extensive modification to form semicircular canals, vestibule and cochlea. Endolymphatic duct developed at 23 days. Posterior semicircular duct appeared first than anterior and lateral. The cochlear duct located ventrally within the developing otic capsule during 24 to 27 days. Utriculosaccular chamber (vestibule) differentiated into utricle and saccule with macula utriculi and macula sacculi respectively; Crista ampullaris developed in the ampulla of canal at 31 days. Thickening of epithelium in the cochlear duct formed organ of Corti by 46 days. Cochlea differentiated into scala vestibuli, scala tymapani and scala media at 69 days. The hair cells of organ of Corti matured first in basal turn at 104 days; cochlea was well developed with 21/2 turns indicated the complete inner ear formation as adult in 140 days sheep fetuses.ThesisItem Open Access STUDY ON PRENATAL DEVELOPMENT OF ADRENAL GLAND OF SHEEP (Ovis aries)(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2016-10) RAJ SEKHAR, U; RAJU, N.K.B(MAJOR); JAGAPATHI RAMAYYA, P; DHANA LAKSHMI, NABSTRACT: The present work was conducted to observe the histomorphogenesis and histochemical changes in adrenal parenchyma. A total of 63 healthy embryos and foetuses irrespective of their sex were collected from pregnant sheep slaughtered from local slaughter houses of Tirupati and were divided into three groups as per their estimated approximate age. The adrenal glands attained a harvestable size around 46-47 days of gestation. At this age, the adrenals were rounded and pin head shaped and pink in colour and in later stages of development the right adrenal was pyramidal and left adrenal was bean shaped. The left adrenal was heavier, thicker and longer than the right adrenal gland in all groups. The primordium of the adrenal was first noted in 38 days old embryo and was placed cranial to metanephron and ventral to aorta. At 54 days of gestation, thick connective tissue capsule was observed. Collagen fibres, reticular fibres and nerve fibres were noticed in the capsule. However, elastic fibres were not noticed in adrenal gland through out the gestation. The mean thickness of the capsule in group II was 69.196μm ± 12.97 and in group III was 96.003μm ± 16.99 respectively. At 54 days of gestation, zona glomerulosa was formed. At 75 days of gestation, two zones were observed in the cortex i.e, outer zona glomerulosa and inner zone fasciculata. The zona reticularis is not distinctly seen in all the age groups. The thickness of the cortex increased steadily with the age of the foetus. The migration of medullary cells through the capsule was noticed at 60 days of gestation. At 100 days of gestation distinct medulla was observed in the centre of the gland. The chromaffin granules number and their size increased as the age advanced. Noradrenaline and adrenaline producing cells were also observed in the medulla. A large medullary vein was noticed in the centre of the gland. Histochemical studies of adrenal gland revealed that glycogen content was more in cortical cells especially in glomerulosa cells. The capsule showed intense positive reaction for PAS whereas cortex and medulla showed moderate to weak PAS reaction. In the present study, an intense reaction for acid mucopolysaccharides was observed in cortical trabeculae. The reaction for acid mucopolysaccharides was very weak or even absent in adrenal parenchyma. The capsule and medulla were completely devoid of lipids whereas cortex showed moderate reaction. The capsule and cortex showed intense reaction and medulla showed moderate reaction for alkaline phosphatase. The capsule and cortex showed weak to moderate reaction and medulla showed intense reaction for acid phosphatase in all the age groups.ThesisItem Open Access ANATOMICAL STUDIES ON HAIR OF INDIAN SPOTTED DEER (Axis axis), BLACKBUCK (Antelope cervicapra) AND ASIAN ELEPHANT (Elephas maximus)(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2012-12) VINAYA SHEELA, S; PURUSHOTHAM, G(MAJOR); PRAMOD KUMAR, D; LAKSHMAN, MABSTRACT : The present study was undertaken on hair samples of Spotted deer, Black buck and Asian Elephant since they are considered as endangered species. Further the former two species are listed under Indian Wild life Act 1972. Six animals were selected from each species from Nehru Zoological park. Hair samples from six different regions viz., neck, back, lateral abdomen, forelimb, hind limb and tail were collected from each animal and processed for microscopic physical observations, cast technique for scale pattern and for SEM (scanning electron microscope) studies. Microscopic structure of hair of spotted deer and black buck comprised of cuticle, cortex and medulla from without inwards. Hairs of tail and back region of elephant had a cortex, cuticle and whereas all other regions lacked a typical medulla. Color variation was observed between the hairs of different species within an individual and also within an individual hair. Color of hairs collected from six different regions varied from colorless to blackish brown in spotted deer, colorless to dark brown in black buck and from light yellowish brown to dark brown in elephant. Tips of hair shafts in spotted deer were frayed in neck, abdominal and tail regions and were blunt in rest of the regions. In black buck hair tips were frayed in neck region, rounded in hind limb region whereas it was pointed in other regions. In elephant, hair tip was rounded in all regions except in the back and forelimb where hair tips were broken. The cuticle was a translucent colorless outer structure of hair shaft but light brown in hair of neck and back regions in spotted deer and in neck of black buck hair. In elephant hair it was colorless in all regions with light blackish brown margin. Smooth cuticular pattern throughout the length of hair was noticed in most of the regions of three species. Serrated cuticle was seen in the tip of forelimb hair in spotted deer, throughout the length of hair in tail region and mid shaft of forelimb in blackbuck. In back region of elephant it was wavy throughout the length. Cross sectional shape of hair shaft of spotted deer varied from oval to round. It was bean shaped in black buck but was rod shaped in the tip, oval, triangular or round near to base of the shaft in hair of tail region and round in the base of neck. Cross sections of hair in elephant were round. Cortex pattern was smooth throughout the length of hair in spotted deer whereas in black buck it was coarse in the tip and mid shaft of abdomen hair. It was coarse in the hair of all regions in elephant except for tip hairs of neck region. Cortical fusi were present in the proximal part of hair in tail region of spotted deer and back region of blackbuck. No ovoid bodies were observed in hair of spotted deer but were seen towards the base of the shaft of back, hind limb region hair in black buck and in the tip of the hair in abdomen and hind limb hair of elephant. Medulla was lattice type in spotted deer hair whereas it was non lattice type in black buck hair. Vacuolated medulla was evident towards base of the shaft in the hair of tail region in black buck. Medulla was absent in the tip and was tapered towards tip of the shaft in spotted deer and black buck hair. Medulla was not evident in the hair of elephant from all regions except in back and tail hair where multiple medulla was noticed. It was fragmentary or trace like towards tip of the shaft in spotted deer and black buck and its margins were scalloped in spotted deer. Scalloped, irregular and straight medullary margins were present in black buck hair. Wine glass shaped tapered medulla, fragmentary or widened towards base of the shaft were seen in spotted deer and black buck hair. Variation in pigment distribution was evident within individual hair of spotted deer and black buck. In former it was uniform, medial and random while in black buck it was uniform and banded and in elephant it was uniform. A significant difference of mean cortical thickness, medullary diameter, and medullary index of hair between spotted deer and blackbuck was noticed. Shaft diameter of three species differed significantly not only between species and different body regions but also within an individual hair. SEM studies revealed difference in scale pattern in the tip, mid shaft and base of an individual hair in spotted deer and black buck. Imbricate scale pattern with overlapped scales were present in the mid shaft and coronal type in the tip of the shaft. They were faint and distantly placed towards base of the shaft, but were compact in the elephant hair. Margins of the scales were smooth to slightly rippled in mid shaft region and towards the base of the shaft in spotted deer whereas it was smooth in black buck and rippled in elephant hair. Trough on surface of hair was an important feature of blackbuck hair that made it easy to differentiate from that of spotted deer hair. Number of scales per 100 μm length of hair was more at the tip in spotted deer (21.55-22.50) and blackbuck (18.05-20.52). In general scale width was more in the base of the shaft and diameter of mid shaft was more than base. Imbricate scale cast pattern was seen in hairs of spotted deer and black buck towards mid shaft and base. Hair tip showed coronal pattern in spotted deer and black buck. Scale cast imprints were not amenable in shaft of elephant hair which indicates adherence of scales to the shaft surface.ThesisItem Open Access PRENATAL DEVELOPMENT OF VERTEBRAL COLUMN, RIBS AND STERNUM OF BUFFALO (Bubalus bubalis)(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2011-09) BHAGYA LAKSHMI, J; JAGAPATHI RAMAYYA, P(MAJOR); Chandrasekhara Rao, T.S; Sri Latha, ChABSTRACT : The study was made on 46 embryos with their age ranging from 41 to 280 days (2.8 to 91.6 cm CVRL) to study the ossification centres in bones of vertebral column, ribs and sternum. The vertebrae, sternum and ribs of buffalo were developed by endochondral ossification. Three different stages were observed during their development i.e stage of mesenchyme, chondrification and ossification. In general the cervical vertebrae were developed from three principal centres of ossification i.e one for the centrum and two for the neural arches. Atlas showed total three ossification centres viz., 2 for neural arches and one separate ossification centre for ventral arch. The ossification centres of neural arches of the atlas were largest among the cervical vertebrae. Axis showed total four ossification centres viz., one each for neural arches, one for body and one separate ossification centre for odontoid process. The locus of ossification for neural arches and body of axis were appeared first at 64 days of gestation in buffalo. Ossification centre for odontoid process was noted first time in anterior cartilaginous mass of axis at 114 days of gestation. Thoracic vertebrae developed from four ossification centres viz., two for neural arches, one for the centrum and separate ossification centre was noted for dorsal spinous process.. The lumbar vertebrae were developed from three ossification centres viz., one each for the neural arches and one separate ossification centre for body of the vertebrae. The transverse processes of lumbar vertebrae developed from neural arches as lateral outgrowth. Sacral vertebrae showed 3 ossification centres for each vertebra i.e one each for neural arches and one for centrum. The first four coccygeal vertebrae developed each from three centres of ossification i.e one for the centrum and two for the neural arches, whereas the more caudal of the group developed from only one centre of ossification. The cartilaginous precursor of sternum was identified first histologically at 54 days as the bilateral cores of cartilage cells. The locus of ossification in the sternal segments was central, unpaired and continued to the area of 7th sternal segment. The 2nd sternebra was the last segment to show ossification and this segment has appeared for first the time at 143 days of gestation. Ossification was first noted in the shaft of the ribs from 2nd to 6th at 59 days and at 64 days all ribs i.e from 1 to 13 showed ossification.The secondary ossification centres have appeared in heads of first 6 pairs of ribs at 155 days and tubercular facets were identified at 181 days radiographically in ribs. In one specimen, the incidence of supernumerary ribs (14th pair) was also noted in the present study.ThesisItem Open Access COMPARATIVE ANATOMICAL STUDIES ON THE OVIDUCT OF DOMESTIC FOWL AND WHITE LEGHORN(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2018-02) TARUN, MODALAVALASA; RAJU, N.K.B(MAJOR); NAGAMALLESWARI, YAMANI; SREENU, MakkenaABSTRACT: The present study was conducted on thirty six apparently healthy birds belonging to six birds each in domestic fowl and White leg horn (WLH) layers in each group. The birds were divided into three groups as group I (chick), group II (laying) and group III (non laying). The average lengths and weights of the oviduct in domestic fowl and WLH were measured. In group I chicks the mucosa was lined by simple columnar epithelium throughout the length of oviduct. In both domestic fowl and WLH of II and III groups the infundibulum consisted of anterior funnel and posterior neck regions. In tunica muscularis the outer longitudinal layer was arranged in a peculiar bundles of smooth muscle fibres so that it helps in peristaltic movement of infundibulum in transporting the grasped ova. The tunica mucosa of magnum was projected into the lumen and formed longitudinal folds, primary folds were very high and given several secondary and teritiary folds. The epithelium was pseudostratified ciliated columnar with non ciliated cells. The entire propria submucosa was occupied by densely packed tubular glands. In mucosa of isthmus the epithelium was pseudostratified columnar with secretory goblet cells and non secretory prismatic cells was observed in the birds of group II and group III. The involutionary changes appeared in the tubular glands of the group III as the disintegration of eosinophilic granules and occurrence of vacuoles in the cytoplasm. In group II the mucosal folds of the uterus were complex by varying in their size. In larger folds several secondary and tertiary folds were also present and some of these secondary and tertiary folds showed anastomosis. The mucosa of vagina formed numerous primary, secondary and teritiary folds that were elongated and thin in all the birds studied. The luminal epithelium was pseudostratified ciliated columnar and the invaginations of this epithelium served as sperm storage tubules. The inner circular layer was strong which formed vaginal sphincter at the opening of cloaca. The serosa was thick with abundant collagen, reticular fibres and numerous small blood vessels in all the birds studied. The secretory cells of lining epithelium of mucosal folds in infundibulum, magnum, isthmus, uterus and vagina showed PAS +ve reaction indicated the presence of mucopolysaccharides in both domestic fowl and WLH of group II. The non secretory cells of the lining epithelium in mucosal folds of oviduct in the birds of both group II and group III showed the glycogen content at the apical regions of the cells. The pyramidal cells of tubular glands in the uterus of domestic fowl and WLH in group III showed a few lipid droplets in the cytoplasm. The intense calcium mineralization was observed at the apical part of secretory cells in the lining epithelium of mucosal folds of the uterus in both the birds of group II.ThesisItem Open Access STUDY ON HISTOGENESIS OF KIDNEY IN SHEEP (Ovis aries)(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2017-08) DURGA PRASAD, DANGETI V.V.N; NAGAMALLESWARI, YAMANI(MAJOR); RAJU, N.K.B.; RAGHUNATH, MABSTRACT: The study was carried out in 45 embryos and foetuses of local Nellore sheep from 20 days to 150 days of gestation to explicate the development of various structures in the kidney. At 20 days (0.7cm CRL) of embryo, the mesonephros located lateral to the testis and occupied larger part of the coelomic cavity. In group I (39.5 days) to group III (150 days) the dorsal surface of both the metanephric kidneys was in contact with psoas major muscle. The metanphric kidneys, in all age groups were varying in colour from light to dark brown. In 20 day (0.7cm CRL) old sheep embryo the pronephros was placed on either side of the dorsal aorta which was surrounded by undifferentiated mesenchymal cells. The pronephros consisted of only one giant glomerulus of 225±1.3μm in size. At 24 days (1.1cm CRL) degenerative changes were noticed in glomerular network due to which vacuolation was noticed between the tuft of glomerulus. In 20 day (0.7cm CRL) old embryos the mesonephric parenchyma was densely packed with tubules, migrating angioblasts and differentiating glomerulus. At 24 days (1.1cm CRL) the mesonephric glomerulus surrounding visceral and parietal layers were demarcated at this age. In 27 days (1.7cm CRL) the manifestation of macula densa of DCT, Juxtaglomerular cells of afferent arteriole and mesengial cells at vascular pole of Bowman’s capsule was observed. At 49 days (7cm CRL) of gestation glomerulus shrinkage was noticed indicating the degeneration process initiated in mesonephros. The ureteric bud of metanephros was formed by evagination of the caudal part of the mesonephric duct in sheep embryo at 20 days of gestation (0.7cm CRL). At 44 days (5cm CRL) of gestation the number of the renal corpuscles were increased and distributed towards periphery from the pelvis. Demarcation between proximal and distal tubules was noticed. Major and minor calyces were apparent at 57 to 60 days of gestation and increased quantity of collagen at the sinus around the major and minor calyces. Loop of Henle was first appeared at 83.5 days, which were well established in juxta medullary nephrons as descending and ascending limbs. In group III the typical cortex and medulla was differentiated as adult kidney and renal corpuscles were still under differentiating stages in the cortical region by 101 days. Papillary ducts were lined by stratified cuboidal epithelium minor calyx was lined by transitional epithelium like adult kidney and smooth muscle were also noticed in the wall of the calyx minor in 115 days of gestation. By 120 days Juxta glomerular cells exhibited the cytoplasmic granules. In group III at 101 days (26cm CRL) the capsule and tubules showed mild PAS positive reaction and the cytoplasm of collecting ducts showed intense PAS positive indicating the neutral mucopolysccharides in the collecting ducts. In group I to group III the renal corpuscles, tubules and collecting ducts showed negative reaction for both acid and alkaline phosphatasesThesisItem Open Access DEVELOPMENTAL STUDIES ON PANCREAS IN SHEEP FOETUS (Ovis aries)(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2016-12) SWETHA, NANDAGARI; NAGAMALLESWARI, YAMANI(MAJOR); RAJU, N.K.B.; HARIKRISHNA, N.V.VABSTRACT: The present study was conducted on the prenatal development of pancreas in sheep foetuses of age 37 to 122 days of gestation. Morphologically pancreas was undifferentiated from 37 days (0.7CRL) to 43 days (3.7CRL) old foetuses. At 38 days of gestation (CRL- 1.5 Cm) histologically dorsal pancreatic lobe was present towards the duodenum and the ventral lobe towards liver. In the pancreatic primordia, ductules were also present, lined by single to double layered cuboidal cells by leaving a wide lumen and few endocrine cells were differentiated in 44 days. During 51 to 52 days of gestation, round bulb like acini without lumen were closely adhered to the ductules. At 55 days, the developing lobules were located towards the periphery of the pancreatic parenchyma. In 61 days, initiation of the interlobular septa with collagen and reticular fibres and islet groups with blood cells were observed in the parenchyma. Nerve fibres were evidently surrounding the forming lobules and also in the interlobular connective tissue in 74 days of foetal pancreas. In 80-84 days , duct system was clearly noticed in the developing exocrine part, intralobular and interlobular ducts lined by cuboidal cells. During 87 to 90 days, developing islets of varying sizes were noticed at the periphery of lobules as well as in the interlobular connective tissue and were separated from the acini by a thin connective tissue capsule At 90 days the apical surface of acinar cells contained cytoplasmic granules and centroacinar cells were distinctly appeared in some lobules with euchromatic nucleus. At 122 days of gestation, lobules were more obvious divided by a thick connective tissue septa and cluster of endocrine cells were surrounded by blood islands which might be the future sinusoids. Histochemical studies revealed that the acinar cells in the lobule expressed moderate reaction for some neutral mucopolysaccharides. Some of the differentiated acini at periphery of the lobule expressed the reaction in 80 to 90 days. Few cells present at the terminal portions of exocrine acini of pancreas were immunologically reactive to insulin antibody. These cells appeared to be beta (β) cells at 90 days. In 122 days immunologically reacted cells against insulin antibody were present between exocrine portions within the lobule.ThesisItem Open Access STUDIES ON THE PRENATAL DEVELOPMENT OF TESTIS IN SHEEP (Ovis aries)(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2016-12) BASAVAIAH, MAACHEPALLI; NAGAMALLESWARI, YAMANI(MAJOR); RAJU, N.K.B; RAGHUNATH, MABSTRACT: The present study was undertaken to elucidate the developmental changes in the testis. The study was conducted on 38 embryos and foetuses of sheep collected from local abattoirs from 37 to 122 days (0.7 to 41 cm CRL) were collected and divided into three age groups basing on gestation periods. In group I, at 42 days of gestation, testes were located in between the metanephric kidneys medially and mesonephros laterally in the lumbar region and scrotal bud was first observed in the inguinal region. At 59 days of gestation, the testes were located at caudal pole of kidney. At 94 days of age, the descent of testes into the scrotum was completed. At 122 days of gestation, testes were located in the scrotal sac. At 44 days of gestation, testes were oblong in shape but testes were changed to oval at 46 days of foetal life later became elongated at 60 days of gestation. The genital ridge was first observed between the mesonephoros and primitive gut in 37 day old sheep foetus. At 39 days of gestation, the gonadal anlages protruded into the coelomic cavity as paired oval-shaped structures on either side of the dorsal mesentery of the hindgut medial to the mesonephros. At 44 days of gestation, mesenchymal cells beneath the germinal epithelium were transformed to tunica albugenia. Sex cords were first appeared at 44 days foetal testes. The dark small cells were modified to form Sertoli cells and were first observed at 46 days of gestation. At 69 days, the lumenization was observed in more number of seminiferous tubules. At 94 days, very few tubules were closely adherent with the endothelial cells and formed blood testes barrier. At 46 days of foetal life, the interstitial endocrine cells gradually modified to form isolated Leydig cells. At 44 days of gestation, the central area of the testis was devoided of sex cords and tailored as mediastinum testis. In group III, the mediastinum consisted of densily packed collagen and reticular fibres in between the rete tubules. At 73 days of gestation, the density of cell clusters in the area of mediastinum testes was increased. Vacuolation was observed in the central area of cell clusters resulted in the initiation of the lumen formation in rete testis. Histochemical studies of testes revealed that in group III at 122 days of gestation, intense positive reaction in the capsule, basement membrane of seminiferous tubules and blood capillaries was identified for mucopolysaccharides. Intense positive reaction was identified in the capsule, basement membrane of seminiferous tubules and blood capillaries for glycogen at 122 days. In group II and III mild reaction for lipids in the capsule was recorded.