THE SEMINAL FLUID. 



alkaloid, as well as by the free diamins. It is these substances that give the odor 

 to the sawdust of macerated bones, and occasionally to stale eggs or pike, and 

 probably also to some plants, such as rhubarb, rhus, berberis. The secretion ot 

 the seminal vesicles (of the guinea-pig) contains a considerable amount of fibrin- 

 ogen. 



The seminal thread (spermatozoon, spermatosoma), 50 /j. long, 

 consists of a flattened pear-shaped head (Fig. 354, i and 2 k), a bodkin- 

 shaped middle segment (m) attached to the broader pole of the head 

 and the thread-like elongated cilium (flagellum or tail) (/), through 

 whose to-and-fro movements the sperm, often rotating on its axis, 

 traverses 400 times its own length in one minute, or from 0.05 to 0.15 

 mm. in one second. This activity is most pronounced directly after 

 ejaculation. 



The head, containing chromatin (mammals), consists of an anterior and a 

 posterior segment. From the posterior segment a process projects like a sphere 

 into the interior of the anterior segment. A delicate membrane covers the anterior 

 segment of the head like a hood. The spermatozoa of some vertebrates possess 

 at the anterior extremity of the head a projection furnished with barbs, which 

 corresponds to the hood. The middle segment of the spermatozoon sometimes 

 presents transverse striations, due to a spiral structure. 



G. Retzius describes the spermatozoon as possessing a special, detached 

 terminal segment of the tail, which represents the extremity of the latter. An 

 axial fiber (Fig. 354, i, <?). surrounded by a protoplasmic sheath, passes through 

 the middle segment and the tail. The sheath is lacking only at the extremity 

 of the tail. The axial fiber consists of two filaments, each of which in turn is 

 made up of numerous primitive fibrils. Also the terminal segment may be re- 

 solved into four fibrils. Some vertebrates possess a marginal filament arising 

 from the middle segment, also an accessory filament parallel to the axial fiber 

 and a steering membrane in advance of the terminal segment. In insects and am- 

 phibia the nonfibrillated axial fiber forms the supporting structure. In some 

 organisms the spermatozoon is still more complicated. Only axial fibers having 

 a fibrillar structure exhibit motility; those not so constructed are motionless. 



The number of spermatozoa in man reaches 60,900 in i cu. mm. ; it is increased 

 after sexual excitement. To each mature human ovule, there are approximately 

 850,000,000 spermatozoa. 



The movement of the spermatozoa is due to the circular, whip-like oscillation 

 of the tail, which at the same time causes rotation about the long axis and is 

 brought about by the protoplasm of the middle segment and the tail. Both 

 of these, even if detached, are capable of movement. Ciliated cells, whose in- 

 dividual cilia consist of numerous filaments lying side by side, swarm-spores in 

 plants and ameboid cells show analogous motility, as transitions between ciliated 

 and ameboid movement have been observed, as in monera. 



Human spermatozoa preserved without heat have exhibited motility after 

 the lapse of nine days; spermatozoa from the guinea-pig after the lapse of eleven 

 days. Permitted to rest passively in the testicle, in the absence of any diluting 

 fluid, the spermatozoa possess no motility. They remain especially active in 

 the normal secretions of the female genitalia. They retain their motility for a 

 considerable length of time also in all normal animal secretions, except saliva. 

 On addition of water they become rolled into rings and cease their movement. 

 Also alcohol, ether, chloroform, creosote, gum, dextrin and vegetable mucus, 

 concentrated solution of grape-sugar, as well as excessively alkaline uterine, 

 and exceedingly acid vaginal mucus, acids and metallic salts and excessively 

 high and excessively low temperature inhibit the activity of the spermatozoa. 

 Their motility is unaffected by narcotics, insofar as they are chemically indifferent, 

 and by solutions of urea, sugar, albumin, common salt, glycerin, amygdalin and 

 other substances of moderate strength ; although these inhibit motility like water 

 if greatly diluted and by abstraction of water if unduly concentrated. 



It is noteworthy that the rest occurring after the action of water, as well as 

 that on gradual cessation of movement, may be terminated by the action of weak 

 alkalies, as may be observed also in ciliated epithelium. Perhaps the alkalies 

 neutralize an acidity of the protoplasm induced by fatigue ; although Engelmann 

 attributes restorative power to small quantities of acid, alcohol, and ether. 



