660 OF SECRETION. 



Kidney. The diameter of the Tubuli is for the most part very uniform; in the natural con- 

 dition they seem to vary from about the l-195th to the l-10th of an inch; but when injected 

 with mercury they are distended to a size nearly double the smaller of these dimensions. 

 When they have reached to within a line or two of the Rete Testis, they cease to be con- 

 voluted, several unite together into tubes of larger diameter, and these enter the rete testis 

 under the name of tubuli recti. The rete teslis consists of from seven to thirteen vessels, 

 which run in a waving course, anastomose with each other, and again divide, being all 

 connected together. The vasa efferentia which pass to the head of the epididymis are at 

 first straight, but soon become convoluted, each forming a sort of cone, of which the apex is 

 directed towards the rete testis, the base to the head of the epididymis. The number of 

 these is stated to vary from nine to thirty ; and their length to be about eight inches. The 

 epididymis itself consists of a very convoluted canal, the length of which is about twenty-one 

 feet. Into its lower extremity, that is, the angle which it makes where it terminates in the 

 vas defcrcns, is poured the secretion of the vasculum aberrans or appendix ; which seems 

 like a testis in miniature, closely resembling a single lobule in its structure. Its special func- 

 tion is unknown. 



b. The Testicles originate, in the Embryo, from the lower part of the Corpora Wolffiana 

 ( 839, c) ; arising from their lower and inner sides, whilst the Kidneys spring from their 

 upper and outer parts. They make their first appearance in the Chick about the fourth day, 

 as delicate striae on the Wolffian bodies ; and at this period no difference can be detected be- 

 tween the Testes and the Ovaria, which originate in precisely the same manner. Like 

 the kidneys, the germ-preparing organs increase in proportion with the diminution in the 

 temporary structures , at first their efferent ducts open into those of the Wolffian bodies, but 

 they are subsequently separated by the formation of a partition, like that which separates 

 the rectum from the cloaca. In the Human embryo, the rudiments of the sexual organs, 

 whether testes or ovaria, first present themselves soon after the kidneys make their appear- 

 ance, that is, towards the end of the seventh week. They are at first much prolonged, and 

 seem to consist of a kind of soft, homogeneous blastema, in which the tubular structure subse- 

 quently developes itself. The Ovary at that period has the same aspect and texture; but its 

 subsequent course of development is different. The Testis gradually assumes its permanent 

 form ; the epididymis appears in the tenth week ; and the gubernaculum, (a membranous 

 process from the filamentous tissue of the scrotum, analogous to the round ligament arising 

 from the labium, and attached to the ovary, of the female,) which is originally attached to 

 the vas deferens, gradually fixes itself to the lower end'of the testis or epididymis. The 

 Testes begin to descend at about the middle period of pregnancy ; at the seventh month 

 they reach the inner ring ; in the eighth they enter the passage ; and in the ninth they usually 

 descend into the scrotum. The cause of this descent is not very clear. It can scarcely be 

 due merely, as some have supposed, to the contraction of the gubernaculum; since that does 

 not contain any fibrous structure, until after the lowering of the testes has commenced. It 

 is well known that the testes are not always found in the scrotum at the time of birth, even 

 at the full period. Upon an examination of 97 new-born infants, Wrisberg found both testes 

 in the scrotum in 67, one or both in the canal in 17, in 8 one testis in the abdomen, and 

 in 3 both testes within the cavity. Sometimes one or both testes remain in the abdomen 

 during the whole of life ; but this circumstance does not seem to impair their function. This 

 condition is natural, indeed, in the Ram. 



867. The fluid secreted by the Testes is thick, tenacious, and of a greyish 

 or yellowish colour. It is mingled, during or before emission, with ildid 

 secreted by the Prostate, Cowper's glands, &,c. ; and it cannot, therefore, be 

 obtained pure, but by drawing it from the testicle itself; hence no accurate 

 analysis can be made of it in the Human subject. The so-called Spermatozoa 

 and Seminal Granules, which form the most important and characteristic parts 

 of the Semen, are so intimately connected with the Reproductive Function, 

 that they will be more appropriately described under that head. It maybe here 

 remarked, however, that they correspond most exactly with other Secretions, 

 in their mode of production ; for, as will be shown hereafter, they are elaborated 

 by cells, which lie within the tubuli, and which rupture so as to set them free, 

 when they are mature ( 902). The peculiar odour which the Semen pos- 

 sesses, does not appear to belong to the proper spermatic fluid; but is probably 

 derived from one or other of the secretions with which it is mingled. The 

 chemical analyses which have been made of this fluid are all defective, inas- 

 much as they do not distinguish the real secretion of the testes from the mucus, 

 prostatic fluid, &c., with which it is mingled. It may be stated, however, that 



