553 MALE ORGANS OF GENERATION. 



very singular and active movement, to which we have already 

 alluded. If a drop of fresh seminal fluid be placed under the 

 microscope, the numberless minute filaments with which it is 

 crowded are seen to be in a state of incessant and agitated motion. 

 This movement of the spermatozoa, in many species of animals, 

 strongly resembles that of the tadpole; particularly when, as in the 

 human subject, the rabbit, &c., the spermatozoa consist of a short 

 and well defined head, followed by a long and slender tail. Here 

 the tail-like filament keeps up a constant lateral or vibratory move- 

 ment, by which the spermatozoon is driven from place to place in 

 the spermatic fluid, just as the fish or the tadpole is propelled 

 through the water. In other instances, as for example in the water- 

 lizard, and in some parasitic animals, the spermatozoa have a con- 

 tinuous writhing or spiral-like movement, which presents a very 

 peculiar and elegant appearance when large numbers of them are 

 viewed together. 



It is the existence of this movement which first suggested the 

 name of spermatozoa to designate the animated filaments of the 

 spermatic fluid ; and which has led some writers to attribute to 

 them an independent animal nature. This is, however, a very 

 erroneous mode of regarding them ; since they cannot properly be 

 considered as animals, notwithstanding the active character of their 

 movement, and the striking resemblance which it sometimes pre- 

 sents to a voluntary act. The spermatozoa are organic forms, 

 which are produced in the testicles, and constitute a part of their 

 tissue; just as the eggs, which are produced in the ovaries, natu- 

 rally form a part of the texture of these organs. Like the egg, 

 also, the spermatozoon is destined to be discharged from the organ 

 where it grew, and to retain, for a certain length of time afterward, 

 its vital properties. One of the most peculiar of these properties 

 is its power of keeping in constant motion ; which does not, how- 

 ever, mark it as a distinct animal, but only distinguishes it as a 

 peculiar structure belonging to the parent organism. The motion 

 of a spermatozoon is precisely analogous to that of a ciliated epi- 

 thelium cell. The movement of the latter will continue for some 

 hours after it has been separated from its mucous membrane, pro- 

 vided its texture be not injured, nor the process of decomposition 

 allowed to commence. In the same manner, the movement of the 

 spermatozoa is a characteristic property belonging to them, which 

 continues for a certain time, even after they have been separated 

 from the rest of the body. 



