64 OBSTETRICAL PHYSIOLOGY. 



of the ovary, in those animals in which the pavilion of the Fallopian 

 tube is large enough to envelop it more or less completely. But in 

 those creatures, such as the Mare, in which the ovary is so voluminous, 

 the pavilion cannot cover it ; and it is not at all unlikely that in this 

 case the rupture of the vesicles occurs at the hilus of the ovary, as the 

 corpora lutea have only been observed at this part. In multiparous 

 animals, the rupture of the vesicles at one period of rutting does not 

 appear to take place simultaneously, but successively. 



The number of Graafian vesicles which come to maturity and rupture 

 at each period of oestrum, depends, with some exceptions, upon the 

 number of young each female brings forth at a birth. The Mare, Cow, 

 and Sheep, having usually only one offspring at a time, only one vesicle 

 ripens during oestrum ; the Goat has most frequently two young, and 

 in this case a vesicle ruptures in each ovary ; while the Pig and 

 Carnivora having several at a birth, a corresponding number of vesicles 

 open, and their contents occupy' each cornu of the uterus. 



The ovum liberated by the bursting of the vesicle is seized by the 

 pavilion of the oviduct, which is applied somewhat closely to the 

 surface of the organ, and is carried down the tube to the uterus, where, 

 if fecundation does not ensue, it remains only a brief period before it is 

 expelled or perishes. The seizure of the ovum, as has been stated, is 

 all the more certain in proportion as the pavilion is large enough to 

 grasp a large surface of the ovary ; this condition is found most 

 developed in the Carnivora. 



CHAPTER II. 

 Fecundation. 



The effective intercourse of the male with the female is followed by 

 certain remarkable changes in the ovum and generative apparatus of 

 the latter, which, at first known as fecundation, conception, or inipreg- 

 iiation, ultimately results in the formation of a new creature possessed, 

 to a certain degree, of individual or independent life. The intercourse, 

 to be effective, depends upon the presence of a healthy ovum in the 

 generative apparatus of the female, and the introduction into this 

 apparatus of the seminal fluid by the special organ of the male. This 

 fluid contains the essential elements known as " spermatozoa " — organic 

 particles of a particular shape, and endowed with motion. For con- 

 ception, it is absolutely necessary that the ovum of the female should 

 be brought into contact with these particles ; though whether this con- 

 tact can occur in the ovisac, prior to its escape, has not yet been defi- 

 nitely ascertained. It is certain that, by reason of their particular 

 movements, and also doubtless through the aid they receive from the 

 special motion of the ciliated epithelium covering certain portions of 

 the lining membrane of the uterus, these spermatozoa, when the uterine 

 opening is patent, are diffused soon after coit^is to the most distant parts 

 of that cavity, and high up in the Fallopian tubes ; though they have 

 never been traced so far as the ovisac. Nevertheless, a very strong 

 argument in favour of their attaining this region, and producing what is 

 called "ovarian" or " tubal impregnation," is afforded in the occurrence 

 of extra-uterine — ovarian or tubal — gestation ; for in this case the 

 spermatozoa must have reached both oviduct and ovary. 



Before the ovum leaves the ovary, changes occur in it which may be 



