252 THE PHYSIOLOGY OF THE 



active ; and it is, perhaps, to stimulate her into increased 

 energy, that he is seen to seize her by the neck with his 

 teeth, while he powerfully embraces her with his fore 

 extremities. 



The cupidity of dealers often tempts them to administer 

 to their stallions stimulants, in order to force the per- 

 formance of an act which is in its nature exhaustive and 

 emaciative. Farcy and glanders are too frequently the con- 

 sequences of this foolish system. 



Conception and pregnancy. — Conception follows, and most 

 mares require copulation but once in order that they may 

 conceive ; which being accomplished the heats, as they are 

 termed, cease, and the animal will afterwards refuse the 

 horse. As the heat recurs at intervals of eight or nine days ; 

 it is usual at those periods to try the mare, by showing her 

 the stallion. 



Impregnation is brought about by means of the semen 

 acting upon the ovum ; but whether the effect is produced 

 by actual contact or by sympathetic influence, has not yet 

 been ascertained ; although the balance is much in favour 

 of the actual transmission of the impregnating fluid through 

 the uterus and oviducts to the ovarium ; which is rendered 

 more probable by the circumstance that the ova of the 

 multiparous animals never reach the uterus, but are retained 

 in the cornua. One of the turgid ovarial vesicles bursts its 

 outer coat, which is received within one of the Fallopian 

 tubes, and conveyed into the uterus, to which it is after- 

 wards found to be universally adherent. A layer of effused 

 lymph is thrown out over the entire surface of the uterus 

 and its connexions : this effusion becomes organized, and is 

 separable into two layers : that layer which is attached to 

 the surface of the womb is called the tunica decidua uteri ; 

 the other, and which becomes reflected over the ovum, was 

 thence named tunica decidua reflexa. When the ovum 

 gradually develops the lineaments of the foetal colt, it will 

 be found surrounded by the reflected portions of the cho- 

 rion ; within which is an inner and finer expansion, called 

 the amnion. Between the amnion and the chorion, in the 

 latter periods of pregnancy, there becomes developed a third 

 membrane, named the allantoid. 



The placenta. — From the attachment of the outer mem- 



