The Cat is pregnant from 50 to 60, 62, or even 64 days, the average 

 being 55 clays or eight weeks. 



SECTION V. GEMELLIPAROUS, PLURIPAROUS OR MULTIPAROUS 



GESTATION. 



Among the domestic animals there are species which are naturally uni- 

 parous — produce only one at a birth ; and others which, in a normal or 

 physiological manner, bring forth two, three, or more at a time, and are 

 therefore designated g3meUiparous or tnidtiparoiis, gestation being known 

 as double, triple, quadruple, etc. As examples of uniparoiis animals, we 

 may give the Mare, Ass, Cow, and Sheep ; while we may cite the Pig, 

 Bitch, and Cat as imiltiparous creatures. As multiparity is normal with the 

 latter, we shall not refer to them, but will allude to those creatures which, 

 naturally uniparous, sometimes bring forth more than one descendant at 

 a time. 



It is seldom that twins are produced by the larger domesticated animals, 

 and particularly by the Mare and Ass, though instances are recorded of 

 these ; while in the Cow, Sheep, and Goat the occurrence of twins, triplets, 

 or even more young creatures at a birth, are not so rare. 



The causes of multiparity are not well ascertained. It may be due to 

 simultaneous ripening of two or more Graafian vesicles, which, rupturing 

 at the same time, allow the escape of the ovules they contain, and which 

 may become impregnated at a single coitus. Or a Graafian vesicle may 

 contain two or more ovules, as Bischoff has witnessed in woman ; and 

 these arriving together in the uterus, may be fecundated at one time. Or 

 it may even happen that the vitelline membrane contains two yolks, as 

 sometimes occurs in the fowl's Qgg ; and as the vitelline mass is the 

 essential part of the ^gg, it is evident that when this contains two of these 

 masses, they ought, if fecundated, to produce two embryos. 



In the first case, as Saint-Cyr points out, each foetus has ordinarily all 

 its annexes distinct and completely independent ; or it may be that the 

 two chorions are fused together, in which circumstance the two fcetuses 

 will then have a common envelope. In the second hypothesis, this fusion 

 of the chorions appears to be the rule, although the envelopes may also 

 be independent ; and in the third case — that of the two vitelluses con- 

 tained in the same vitelline membrane — not only the envelopes, but also 

 the foetuses may become united more or less closely, and thus give rise 

 to double monsters, 



Finally,_it is also possible that two ovules may become detached from 

 the ovarian cluster, though not simultaneously, but successively ; and be 

 fecundated, one after another, at two consecutive copulations within a 

 brief period. Occurrences of this kind, by no means rare, have beer 

 wrongly adduced as instances of superfoetation. 



Mare. 



Of all the domestic animals, the Mare is the one which least frequently 

 brings forth more than a single creature at a birth ; and Saint-Cyr has 

 only been able to collect fourteen instances, though we have been more 

 fortunate. Rueff admits that one case of gemellar gestation may occur 

 in this animal in every 250 normal cases; but that the young are nearly 



