436 COVERINGS OF THE TESTIS. [SECT. 1 98. 



in advanced age, yet spermatozoa and even capability of pro- 

 creation are not unfrequently found in men sixty, seventy, or even 

 eighty years old. Duplay found spermatozoa thirty-seven times 

 in fifty-one men between sixty and eighty years of age. In twenty- 

 seven of these, they were quite normal, in the others, deformed 

 by the loss of their tails. After diseases, the spermatozoa are just 

 as frequently found as not ; and all that can be said with re- 

 ference to the cause of their absence in such cases is, that it seems 

 to depend chiefly upon the disturbance of nutrition. 



§ 198. Coverings, Vessels, Nerves of the Testicle. — The testicle, 

 together with its fibrous coat and a part of the epididymis, are 

 directly inclosed by the special serous tunic (tunica vaginalis pro- 

 pria, fig. iJJ,b df) . This is a thin serous membrane, which was in its 

 origin a part of the peritoneum, and corresponds with it in structure. 

 Its epithelium is composed of a layer (croo5'" in thickness) of clear 

 polygonal cells, croc^'" to croo8" in size, with beautiful nuclei, 

 and here and there a few pigment granules of yellowish hue. On 

 the testicle itself, the epithelium is immediately situated upon the 

 fibrous coat, being inseparably blended therewith, and constituting 

 the so-called tunica adnata testis, or the visceral lamina of the 

 tunica vaginalis propria. Over the epididymis, however, the serous 

 membrane can be distinctly isolated, as in the parietal lamina of 

 the tunica vaginalis, and it here consists of dense connective tissue, 

 intermingled with elongated nuclei. The general vaginal tunic of 

 the testicle, tunica vaginalis communis is a dense membrane of 

 some thickness, which closely surrounds the serous sac, and forms 

 a ' common ' envelope to the testicle, the epididymis at its lower 

 end, and the spermatic cord. On the testicle, it consists of firm 

 connective tissue, but higher up it is a looser net-work, and has 

 many elastic fibres. Between this envelope and the parietal layer 

 of the serous membrane, and on the epididymis, is found a layer 

 of smooth muscular fibre, spread over the lower two-thirds of the 

 testicle. This is firmly connected, both with the common envelope 

 just described and the proper tunica vaginalis, and may be 

 called the inner muscular coat of the testicle ; the cremaster, 

 which is made up of transversely striated fibres, being inserted into 

 the outer side of this muscular layer. Finally, the whole of the 

 parts hitherto mentioned are enclosed in the scrotum, which con- 

 sists of the tunica dartos (§ 36), or outer muscular coat of the 

 testicle, loosely connected with the common vaginal tunic, and the 



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