44 THE DISCHARGE OF OVA 



7. Function of the spermatozoids. 



That the spermatozoids are normal and essential elements of the semen, 

 is evident from many facts. These facts are the presence of such par- 

 ticles in the seminal fluid of all classes of animals, (the Infusoria being the 

 only class in which they have not been discovered) ; the large proportion 

 they constitute in the bulk of the seminal fluid, (the fully formed semen 

 consisting almost wholly of a mass of spermatozoids) ; their close connection 

 with the states of puberty and of heat in the males of all animals (they 

 being first formed at the age of puberty in the human subject, and being 

 periodically produced at each time of heat in animals, while in the in- 

 tervals they disappear) ; the presence of these spermatozoids on or 

 about the ova which are observed immediately after fecundation, (Barry, 

 Bischoff, Pouchet, and other recent observers,) and, lastly, the apparently 

 conclusive proof obtained by Prevost,* who filtered frog's semen by 

 means of a bladder, and found that the filtered fluid had not the power of 

 impregnating ova, while the spermatozoids, which did not pass through the 

 filter, still retained the fecundating property. 



Bischoff and Valentin, however, think that the fecundating principle 

 itself is contained in the fluid part of the semen, which passes by im- 

 bibition through the zona pellucida ; and that the function of the sper- 

 matozoids is two-fold, first, by their energetic movements to act as carriers 

 of the seminal fluid to its destination at the ovum ; and, secondly, by the 

 same active movements, and probably also by some chemical quality, to 

 maintain in its integrity the due mixture and composition of the liquor 

 seminis : acting, in this latter respect, a part somewhat analogous to 

 that performed by the corpuscles of the blood towards the liquor 

 sanguinis. 



OF THE DISCHARGE OF OVA FROM THE OVARIES.t 



THESE processes have become the subjects of much discussion during 

 the last few years, and the following questions relating to them have been 

 especially examined. 



1 . What determines the discharge of ova from the ovary t 



2. Is the presence of a corpus luteum in the ovary a sure evidence of 

 previous impregnation *? 



3. What is the nature and purpose of the function of menstruation 1 

 Respecting the first two questions, the opinions of physiologists have for 



a long period been extremely various and unsettled. Of late years, how- 

 ever, the opinion has been gaining ground that the discharge of ova from 

 ovary is independent, not only of impregnation, but also of sexual intcr- 



* L'Institut, 1840, No. 362. 



t Book viii. sect. ii. chap. v. p. 1481, of Muller's Physiology. 



