62 OBSTETRICAL PHYSIOLOGY. 



CHAPTER III. 



Sterility. 



Hitherto we have been treating of successful fecundation as if it was 

 always a sure result of the coupling of the male and female sexes at a 

 certain period. Successful fecundation, however, is not always the case, 

 and in some species — particularly the equine — sterility, temporary or per- 

 manent, in the female is far from being uncommon, and is sometimes 

 serious. Sterility or infecundity depends on numerous causes, to some 

 of which we must allude, as in distinguishing their presence we may be 

 able to remove or counteract them. 



It is difficult to ascertain the extent to which it prevails, especially in 

 the larger and more important animals. In the Stud Book, it is shown 

 that among thorough-bred Mares the percentage of those which carry foal 

 is 73*36, and those which abort or are infecund 26*64. I^ the studs of 

 France the fruitful Mares are 59*57, and the unfruitful ones 40*43 per 

 cent. The Duke de Guiche gives 68 per cent, of fecund Mares. At the 

 haras of Pin, during a period of twenty years, there was a percentage of 

 68*27 fecund Mares, abortions 5*06, non-fecund 26*67 \ while at the Pom- 

 padour haras, where oriental horses were chiefly bred, the births in three 

 years were 79*55, abortions 2*27, and non-fecunds 20*45. 



In the Cow, the fecundations appear to average about 79 per cent. 



With the Sheep, sterility or infecundity is not so common. Rueff, at 

 Hohenheim, found among 8500 sheep, only 740, or 8 per cent, unfruitful. 



Sterility may depend upon organic or physical causes, and may amount 

 to permanent impotence, more particularly when congenital, and located 

 in the generative apparatus. Monstrosities, hermaphrodites, animals in 

 which one or more important organs of the sexual apparatus are absent, 

 and hybrids, are generally permanently sterile.* 



Prolonged continence and old age is not an unfrequent cause of infe- 

 cundity, as is witnessed in Mares which have worked for many years in 

 towns, and then been transferred for breeding purposes. 



Change of climate has in many cases a marked influence on fecundity ; 

 sometimes putting it altogether in abeyance, and at others rendering the 

 animals infecund for only a longer or shorter period. It may also be im- 

 paired, or suspended temporarily or permanently, by abuse of the gener- 

 ative functions, bad hygiene, etc. 



It may likewise be due, though temporarily, to premature or tardy 

 coition when the generative organs are not in a physiological condition 

 for conception, or when they are in an irritable, abnormal state. Under- 

 fed or over-fed animals generally do not breed so readily as those which 

 are in moderate condition ; fat animals are especially unfruitful. Excit- 

 able, vicious Mares are less likely to procreate than those which are of an 

 equable and gentle disposition. The latter are often impregnated at one 

 attempt ; and it has been observed that with Mares accustomed to work, 

 active exertion, even to produce fatigue, before being put to the horse, is 

 favorable to conception. So it is that the Arab submits his Mare to a 



* There are exceptions to this rule. Several well-authenticated instances are recorded in which the 

 soliped mule has bred, as well as other hybrids. 



