ORGANS OF THE BODY. 5G3 



we have the head or nucleus (1), the middle portion or remainder of the 

 cell-body (2), and the filament, the elongated cilium (3). 



285. 



The most striking and important peculiarity of the seminal elements, 

 and one recognised as such ever since their discovery, consists in their 

 movements. These, which were in olden times accepted as a proof of 

 their independent individual life (whence the name " spermatozoa") 

 appear to be very nearly allied to the phenomena of ciliary motion ( 99), 

 and, like the latter, baffle at present all explanation. 



If semen be taken from the seminal tubes of some freshly slaughtered 

 mammal, it will be found, as a rule, that the movements in question have not 

 yet commenced. But if a drop of the fluid, immediately after emission from 

 the urethra, be placed upon a glass slide under the microscope, innumerable 

 spermatozoa are observed moving in all directions in the utmost confusion. 



Closer inspection shows us that the individual elements of the semen 

 execute a series of movements, consisting in alternate flexion and exten- 

 sion, and undulating motions like those of the lash of a whip, by means 

 of which the whole structure is propelled from place to place. Though 

 tempted for a moment to compare this with the independent hurrying to 

 and fro of a host of infusoria, we very soon observe the most marked 

 points of distinction. We miss, in the first place, the spontaneity of the 

 latter organisms, that swimming in definite directions and avoidance of 

 obstacles which characterise their movements ; also that momentary 

 acceleration and slackening in pace. The rate of progression moreover of 

 the spermatozoa is by no means very great, several minutes being consumed 

 in advancing even the distance of an inch. Like the motions of the cilia, 

 those of the seminal filaments commence, after a time, to decrease in rapidity 

 and the structure dies. We remark the intensity of the whip-like undu- 

 lations of the fibre growing less and less, until at last the movements of 

 the latter cease to propel the spermatozoon any farther, and all evidences 

 of life become extinct. 



Let us now consider the conditions of these movements. Their dura- 

 tion, in the interior of the male organs of generation or in emitted semen, 

 varies in these different classes of animals. In birds they cease most rapidly, 

 often within a quarter of an hour. Among the mammalia they persist 

 for a much longer period, at times almost for a whole day. Thus in 

 human semen, after pollution, the spermatozoa may be observed still to 

 retain the power of motion sixteen or twenty hours after emission. 

 Among the Amphibia they last much longer, and in fish longer than in 

 any other animals. Here they may be seen under favourable conditions 

 four days after the discharge of the semen (Wagner). We are thus 

 reminded again of ciliary motion. If the temperature be reduced to 

 below freezing-point, the movements of the spermatozoa cease ; but even 

 after remaining four days in a congealed state they may regain their power 

 of locomotion on being warmed. Cooled down to 17 C., they die ; as 

 also on being heated up to + 50 C. (Mantegazza) . 



As to the effects of the addition of other fluids to the semen, we find 

 that indifferent matters of a certain average concentration, as, for instance, 

 solutions of sugar, urea, glycerine, and neutral salts of the alkalies and 

 earths, may be added without arresting the motion of the spermatozoa, 

 while very dilute solutions cause their destruction. Very concentrated 

 fluids also prevent by their viscidity any play or motion in the filaments. 



