1022 



THE MALE ORGANS OF GENERATION. 



the modified nucleus of the spermatid, and consists chiefly of chromatin, and so 

 stains readily with nuclear reagents ; it is covei'ed by a thin cap of protoplasm. 

 The body is a short cylindrical or conical piece, intervening between the head and 

 tail, and is therefore sometimes spoken of as the intermediate segment. The tail 

 is about four times the combined lengths of the head and body ; its terminal part 

 is extremely fine, and is named the end-piece. Contained within the body and tail 

 is an axial filament, surrounded, except in the end-piece, by a thin layer of proto- 

 plasm ; this axial filament terminates just below the head in a rounded knob or 

 button. In virtue of their tails, which act as propellers, the spermatozoa, in the 

 fresh condition, are capable of free movement, and if placed in favorable surroundings 

 (e. g., in the female passages) may retain their vitality for some days or even weeks. 



VESICUL^I SEMINALES. 



The Seminal Vesicles are two lobulated membranous pouches placed between the 

 base of the bladder and the rectum, serving as reservoirs for the semen, and secreting 

 a fluid to be added to the secretion of the testicles. Each sac is somewhat pyramidal 



Right Ejaculatory 



FIG. 568. Base of the bladder, with the vasa deferentia and vesiculse seminales. 



in form, the broad end being directed backward and the narrow end forward toward 

 the prostate. They measure about two and a half inches in length, about five lines 

 in breadth, and two or three lines in thickness. They vary, however, in size, 

 not only in different individuals, but also in the same individual on the two sides. 

 Their upper surface is in contact with the base of the bladder, extending from near 

 the termination of the ureters to the base of the prostate gland. Their under surface 

 rests upon the rectum, from which they are separated by the recto-vesical fascia. 

 Their posterior extremities diverge from each other. Their anterior extremities are 

 pointed, and converge toward the base of the prostate gland, where each joins with 

 the corresponding vas deferens to form the ejaculatory duct. Along the inner 

 margin of each vesicula runs the enlarged and convoluted vas deferens. The inner 

 border of the vesiculse and the corresponding vas deferens form the lateral 

 boundaries of a triangular space, limited behind by the recto-vesical peritoneal 

 fold ; the portion of the bladder included in this space rests on the rectum. 



Each vesicula consists-of a single tube, coiled upon itself and giving off several 

 irregular caecal diverticula, the separate coils, as well as the diverticula, being con- 

 nected together by fibrous tissue. When uncoiled this tube is about the diameter 

 of a quill, and varies in length from four to six inches ; it terminates posteriorly in 



