288 THE ANATOMY OF THE HORSE. 



This is termed the corpus Highmori, or mediastinum testis ; and between 

 it and the inner surface of the tunic numerous fine trabeculse 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 trabeculae, the 

 blood-vessels 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 mediastin\im, 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 perforate 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 — spermatoblast 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 

 columnar ciliated lining. 



THE PEEPUCE. 



In its non-erect state the anterior, free, or protrusible part of the 

 penis of the horse is entirely concealed from view, being accommodated 

 within a loose tubular involution of skin, which is ordinarily termed the 

 "sheath," or, in anatomical language, the prepuce. This cutaneous 

 tube, however, is not exactly homologous with the part of the same 

 name in human anatomy, the prepuce of man being represented in the 

 horse by a second short tube which lies within the so-called sheath, and 

 immediately surrounds the free extremity of the penis when that organ 

 is non-erect and fully retracted. This inner tube may therefore be 

 termed the prepuce proper, or the inner prepuce, in contradistinction 

 to the sheath or outer prepuce. The relationship of these two tubes 

 to one another will be understood from Fig. 40, in which, however, the 

 penis is not fully retracted. 



The Sheath consists of two layers — an external, similar to the sur- 

 rounding integument, with which it is continuous; and an internal, 

 continuous with the former at the entrance to the tubular cavity of 

 the sheath. The inner layer of the sheath is composed of a coarsely 

 wrinkled and usually black pigmented skin, differing from the outer 



