176 ANATOMY OF THE DOMESTIC FOWL 



Structure. — The testicle is surrounded by a thin fibrous capsule, 

 which, in the mature cock, is very vascular. This capsule sends 

 into the interior of the gland, septa which form the framework, 

 or supporting structure. This framework forms the spaces in which 

 are located the glandular substance. The glandular portion consists 

 of the tubuli seminiferi, which are lined with cubical cells. The 

 framework supporting these tubules gives passage to arterial 

 branches of the spermatic artery, which furnish an abundant blood 

 supply; the framework also supports the veins returning the blood 

 from the testicle. The seminiferous tubules end in blind extremities 

 in the epididjonus or globus minor, and imite in the seminiferous 

 canals. All arteries, veins, lymphatics, and seminiferous tubules 

 enter or leave through the globus minor at the attached portion of 

 the testicle. The epididymis is made up largely of convoluted 

 tubules which are the continuation of the secreting tubules of the 

 globus major. The walls of the tubules of the globus minor become 

 thicker and are provided with smooth muscle cells in addition to 

 the connective tissue and endotheUal lining. The convoluted 

 tubules empty into the vas deferens. The epidid3Tnus is covered 

 by the fibrous capsule; which corresponds to the tunica albuginea 

 of mammals and may be considered as a reflection or modification 

 of the visceral peritoneum. 



The substance of the testicle is very soft; in fact, it may be said 

 to be of the consistency of encephaloid material. It is made up 

 of secreting tubules in which are foimd the spermatozoa; it also 

 contains cells which produce an internal secretion, or hormone. 

 There is also produced some fluid in which the spermatozoa float, 

 the whole material manufactured constituting the semen. 



The spermatozoa, oi the fowl are provided with long cylindrical 

 bodies, which may be straight or wavy (Fig. 55, A). The body 

 of the spermatozoon is obtuse anteriorly, and posteriorly, tapers 

 into a filimentary tail, or flageUum, of varying length, by the aid of 

 which the spermatozoon moves about in the fluid. 



The histological structure of the testicles of the baby chick at 

 hatching is approximately one-half white fibrous connective tissue. 

 The seminal tubules are small and widely distributed among the 

 connective tissue. The cells of these tubules possess rather large 

 nuclei, round in shape, with Unin network and chromatin granules, 

 typical of resting germ cells. As the bird develops the testicles 



