10 



The Male Reproductive Organs include the penis and testes, 

 together with the excretory passages which connect the testes with 

 the urethral canal. These excretory duets include the epididymis, 

 vas deferens, and seminal vesicles. Posterior to their termination 

 in the urethra, there aro connected the ducts of the prostate gland 

 and the bulbo-urethral or Cowper's glands. 



Testes : The testicles of the bull are relatively large. Vaiying 

 with the size and age of the animal they measure from fourteen to 

 seventeen centimeters in length, including the epididymis, and 

 from six to eight centimeters in diameter. Each testicle is en- 

 closed within a serous sac, the tunica vaginalis, whose 

 visceral layer is very intimately fused with the underly- 

 ing covering of the organ, the tunica albuginea. The tunica 

 albuginea is quite thin and consists of connective tissue 

 which is rich in elastic fibres. Muscular tissue is not present as it 

 is in the case of many mammals. Inside the tunica, and closely 

 attached to, though separated from, the parenchyma by a thin 

 layer of connective tissue, is a laj-er of very loose connective 

 tissue, M'hich because of its rich supply of blood vessels is termed 

 the tunica vasculosa. The parenchyma is of a yellowish gray 

 color, and of a rather soft consistency. It is made up of the semi- 

 niferous tubules, rete, and the connective tissue stroma, the medi- 

 astinum testis. On section, the mediastinum appears as the center 

 or axis of the entire organ. It is star-shaped, and radiates connect- 

 ive tissue septa out into the parenchyma to support and separate the 

 tubule.^. Ellenberger states that the testis of the bull and all 

 ruminants lacks a closed system of interlobular septa, because of 

 the feeble development of the connective tissue. 



The principal blood vessels and rete tubules are found in this 

 structure, the function of the latter being to connect the seminifer- 

 ous tubules and the efferent tubules of the epididymis. The 

 epithelium of the rete is quite irregular. — consisting in places of 

 a single layer ; in others, of two layers. At some points there are 

 formed groups of several cells lying over one another, with swollen 

 liomogeneous basal cells, which sometimes form projections into the 

 lumen. 



The interstitial tissue, besides conveying the blood vessels to the 

 organ, contains many " interstitial cells.'-' These cells are rela- 

 tively sparse in the adult bull, and are comparatively delicate, 

 slightly granular, often shuttle-shaped, with a rather small nucleus. 

 Embryologicnlly they are derived from a syncitium arising from 

 the mesothelium of the genital ridge, differentiating out by growth 

 of the cytoplasm. They contain large quantities of fat, and 

 elaborate the internal secretion of the testis. This secretion gov- 

 erns the development of the secondary sexual characters, and has 

 a profound influence on the general body metabolism, and develop- 

 ment of the skeleton. The interstitial cells appear early in 

 embryonic life even before there is any differentiation of sex, and 



