280 THE ANATOMY OF THE HORSE. 



between it and the inner surface of the tunic, numerous trabeculaj pass, 

 forming a framework for the gland, and dividing it into a number of 

 conical compartments, or lobules, which lodge the seminal tubules. On 

 the inner surface of the tunica albuginea, and on its trabeculse, the 

 bloodvessels are distributed, forming the tunica vasculosa. 



Each seminal tubule begins either with a blind extremity, or by anas- 

 tomosing with an adjacent tubule. The tubes are highly convoluted 

 until they approach the mediastinum, where they unite to form a series 

 of straight tubes — the tubuli recti, which enter the mediastinum and 

 form in it a network — the rete testis. From this network arise a number 

 of tubes termed the vasa efferentia, which peiforate the tunica albuginea 

 above the anterior end of the testicle. On leaving the gland, these 

 become convoluted, forming little masses known as the coni vasculosi ; 

 and they then unite with one another until there results a single excre- 

 tory tube, whose convolutions make up the globus major, body, and 

 globus minor of the epididymis. The seminal tubules are composed of 

 a membrana propria and an epithelial lining. The epithelium is 

 arranged in several layers, and through the agency of the innermost 

 cells — sjyermatoblast cells — the spermatozoa of the semen are produced. 

 The tubuli recti and rete testis are lined by a single layer of columnar 

 epithelium. The tubes of the vasa efferentia and epididymis have a 

 wall that contains non-striped muscular fibres, and they possess a colum- 

 nar ciliated lining. 



THE PREPUCE. 



The pi-epuce, vulgarly called the " sheath," is the involution of skin 

 which lodges tlie free portion of the penis when that organ is non- 

 erect. In this condition it consists of tAvo layers — an external, similar 

 to the surrounding integument, with which it is continuous; and an 

 internal, which is intermediate in texture between skin and mucous 

 membrane. The latter layer is smooth, destitute of hair, and provided 

 with numerous preputial glands, which secrete a strong-smelling sebaceous 

 material. This material facilitates the protrusion of the penis during 

 erection; and, ordinarily, it accumulates in considerable amount within 

 the prepuce. These two layers are continuous with one another at the 

 orifice of the preputial cavity, and at the posterior end of the cavity the 

 inner layer is continuous with the investment of the penis. Towards 

 the orifice of the perputial cavity, two rudimentary tubercle-like teats 

 are sometimes found. Lay hold of the extremity of the penis, and pull 

 it forcibly forwards, at the same time pulling the prepuce backwards. 

 This will obliterate the prepuce, as in erection, in which condition the 

 inner layer of the pi'epuce becomes a part of the covering of the penis. 



Directions. — While the penis is pulled forwards out of the prepuce, 

 carry a mesial incision through the skin from the perinaium to the 



