MALE ELEMENTS OF GENERATION. 885 



These elements are developed within the seminiferous tubes; and they differ, not so much 

 in their mode of development, as in their form, in different animals. AVe shall describe, 

 however, only the spermatozoids of the human subject. 



If we examine a specimen of the fluid taken from the vesicular seminales of an adult 

 who has died suddenly, or the ejaculated semen, we find that it contains, in addition to 

 the various accidental or unimportant anatomical elements which we have mentioned, 

 innumerable bodies, resembling animalcules, which present a flattened, conoidalhead and 

 a long) tapering, filamentous tail. The caudate appendage is in active motion, and the 

 spermatozoids move about the field of view with considerable rapidity and force, pushing 

 aside little corpuscles or granules with which they come in contact. This is supposed to 

 be an indication of the vitality of the spermatozoids, which are not thought to be capable 

 of fecundating the ovum after their movements 

 have ceased. Under favorable conditions, par- 

 ticularly in the generative passages of the fe- 

 male, the movements continue for days ; and 

 this fact is important, as we shall see here- 

 after, in its bearing upon the limits of the time 

 of fecundation. 



Microscopical examination does not reveal 

 any very distinct structure in the substance 

 of the spermatozoids. The head is about 

 WTO of an inch long, ^Vs of an incn broad, 

 and Yvfans f an mcn m thickness. The tail 

 is about ^i of an inch in length. La Vallette 

 St. George has found, in man and many of the 

 inferior animals, the "intermediate segment" 

 described first by Schweigger-Seidel, though 



L-. M.t a v 0-11 .4.1 * FIG. 284 Human spermatotolds ; magnified 800 



he does not agree with Schweigger-Seidel that diameters. (Luschka.) 



this portion is motionless. The length of the 



intermediate segment is about ^Vs of an inch. It is usually described as the beginning 



of the tail ; and the only difference between this and other portions is that it is a little 



thicker. 



Water speedily arrests the movements of the spermatozoids, which may be restored 

 by the addition of dense saline and other solutions. All of the alkaline animal fluids of 

 moderate viscidity favor the movements, while the action of acid or of very dilute solu- 

 tions is unfavorable. The movements are suspended by extreme cold, but they return 

 when the ordinary temperature is restored. 



Before the age of puberty, the seminiferous tubes are much smaller than in the adult, 

 and they contain small, transparent cells, which, in their form and arrangement, resemble 

 epithelium. As puberty approaches, however, the tubes become larger, and the evil-con- 

 tents increase in size. At this time, there seem to be two kinds of cells; an epithelium, 

 in the form of irregularly-shaped cells, lining the tubes, and rounded cells containing one 

 or more nuclei, some of the cells appearing to be in process of iegmentRtioiL Many o 

 the cells lining the tubes present a rounded portion, with a lanre, clear nucleus appIU 

 the tube-wall, each with a caudate prolongation projecting into the tube, 

 the projections from the different cells anastomose with each other, forming a k; 

 work. In the central portions of the tubes of the adult, are rounded v, 

 rf, of an inch in diameter, each containing from two to twenty transparent nnc 

 uring from ^ to ^ of an inch. In these, which are called the iemind C 

 boid movemlnte havSbTen observed. The large vesicles with multiple nuclei are th, 

 of development of the spermatozoids. The nuclei of the veriota appeal- 

 formed into the heads of the spermatozoids, and the filamentous appendages, winch ar, 

 seen in the vesicles in various stages of formation, are developed gradually. 



