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to resist heat, and other properties are augmented, at least in the 

 case of the guinea pig, rat, and mouse." To the secretion is then 

 added the product of the vesicles, Avhich contributes markedly to 

 its fluid content, nourishes the sperms, and supplies the ferment 

 which induces clotting of the semen when ejaculated. This is 

 very important because the clot formed in the vagina protects 

 the delicate spermatozoa from the hostile acid vaginal secretion. 

 The prostate likewise adds bulk and nourishing substances, besides 

 stimulating the spermatozoa to fuller and more lasting motility. 

 The addition of the spermin is perhaps unimportant. The func- 

 tion of the secretion of the Cowper's glands, which is added at this 

 time, is problematical. It does, however, have a diluting action on 

 the semen. Perhaps its secretion is poured out prior to ejacula- 

 tion so as to lubricate the canal and prepare the way for the semen. 

 Fish (28) has demonstrated by means of darkfield illumination, 

 the presence of numerous minute particles or ultraparticles in this 

 fluid. Their character and significance are matters of conjecture, 

 but it would seem as though they were not identical with the 

 "chylomicrons" or fat particles found in the blood by Gage. Per- 

 haps further researches wall reveal some intimate connection be- 

 tween the number present in a field, and the relative potency of 

 the animal. 



Each portion of the tract furnishes some essential element to 

 the mixed product which is so remarkably adapted both as ^ a 

 vehicle for the ejaculation of the spermatozoa, and as a fluid in 

 which their motility is initiated and maintained. Any derange- 

 ment of one part is fraught with danger to the existence of viable 

 spermatozoa, and the continuation of full fertility on the part 

 of the animal. The physiology of each contributing gland must 

 be borne in mind at all "times. AValker (31) investigated the fer- 

 tility of the semen of the dog, taken from various parts of tho 

 tract. His results were: (1) semen from the testicle and head of 

 the epididymis showed no motility, (2) semen from the tail of 

 the epididymis showed some motility in the more fluid contents 

 of the preparations, (3) semen from the vas deferens appeared 

 about the same, (4) a mixture of epididymis semen and pros- 

 tatic secretion showed active motility, and (5) likewise in a mix- 

 ture of epididymis semen, though only in thase places where the 

 fluids had become well mixed. 'My observations, however, differ 

 in one respect with regard to the Inill, as I have found full motility 

 of the spermatozoa from the epididymis, but it is not so lasting as 

 when augmented by the addition of the prostatic fluid. Boettcher 

 (32) concludes: "that the secretion of the accessory male genital 

 organs possesses a protective colloid, which (1) hinders the sper- 

 matozoid action of the vaginal secretion, at least until the sperms 

 have time to reach the interior of the uterus which is an alkaline 

 reaction, (2) that it makes the ejaculate more voluminous, so that 

 by cohabitation, a very good part of the vagina becomes moistened, 

 and the spermatozoa become distributed over the greater part 



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