Ladukar, O. N.Zade, B. A.2017-07-102017-07-102007http://krishikosh.egranth.ac.in/handle/1/5810024783The present study was conducted on testis of dogs collected from 60 healthy stray: dogs from sterilization centre of Nagpur city (NGO) and carried to the laboratory in ice box. These were divided in three groups , Group -l (0-6 months ), Group-ll (6-12 months ) ,i I Group-lll (12 months onwards The samples of testis collected were subjected for gross anatomical examinatiory to record their colure, weight, volume, length, width, thickness and circumference .The histological structure of testis of dog was studied from section stained with haematoxylin and Eosin for normal structure ,VanGieson's for collagen fibers, Verhoeffs method for elastic fibers and Masson's trichrome for collagen fibers .ln the testis of dog of different age group the presence of glycogen , mucopolysaccharids ,alkaline phosphatase, acid phosphatase was ascertained by periodic Acid Schiffs methods , alcian blue pAS method, Mowry,s colloidal iron stain, Gomoris for alkaline phosphatase and Gomori's modified lead Nitr.ate method for acid phosphatase . The testis was enclosed in thick connective tissue capsule .The thickness of tunica albuginea was more in group -l than Group-ll but was again thick in adult age"or dogs .The tunica vasculosa layer is more thick in group I and lll as compared to group-ll. The different stages of sex cells /spermatogenic cells are observed at different age groups. ln the first group the precursors of primary spermatogonia i.e. gonocytes and precursors of Sertoli cells were observed ' ln group-ll showed 7 stages of different spermatogenic cells, wrrite iin group-lll the stages of cells observed upto the 3 to 7 years and beyond 7 to g years tfre spermatogenic cells or germinal epithelium was decreased. The Leydig cells wgre undifferentiated in group-l and they become active in group-ll and in group -lll. They wjre arranged in the pockets, sheath, row and single also. The first group sex cords are completely filled by luminal matrix but as the age advanced the germinal epitheliqm thickness was increased and luminal matrix disappeared. The lumen was first appeared atis % months of age in testis and complete lumen with active stages of spermatogenic cells was noticed at 9 months of age indicated the proper age of sterilization in dog. The histoenzymic study of testis of dog showed varying intensity of activity of glycogen, mucopolysacchradies, alkaline phosphatase, acid phosphatase at different ages in dog' However, the acid phosphatase and Mowry's colloidal iron stain activity was overall very low in the testis of all age groups. The Biomerical and Micrometrical observation dt testis of different age groups indicated the significant differences in the different age groups of dogs.ennullThesis