858 Veterinary Obstetrics 



of the lacerated tissues. After a time the lacerated wounds heal, 

 with cicatricial deformity. There is no reunion of the divided 

 parts, but each portion separately granulates and heals, leaving 

 the perineum divided. The feces constantly fall into the vulva, 

 from which they drop in an involuntary manner, after causing a 

 chronic irritation and thickening of the mucous membrane. If 

 the animal is moved at a rapid pace, thete is an involuntary pas- 

 sage of air in and out of the cloaca, which causes a repulsive 

 sound, and as the air is involuntarily forced out it usually carries 

 with it particles of fecal matter. 



The causes of rupture of the perineum may be divided into three 

 important groups. 



1. The misdirection of a fetal extremity, by which it becomes 

 deviated upward and is forced through the roof of the vagina 

 into the rectum, to eventually appear in most cases through the 

 anal opening. The other fetal extremities pass through the vulva, 

 and thus, as the fetus is forced along by the expulsive efforts, 

 the complete rupture of all tissues between the vulva and anus 

 posterior to the perforation inevitably follows. When the owner 

 or obstetrist is present, and notes the threatened injury in time, 

 the diverging foot or head may be pushed back into the vagina 

 from the rectum, and the delivery brought about in the usual 

 way, leaving a more or less extensive tear in the recto-vaginal 

 partition. Cases are recorded in which the entire fetus has 

 passed into the rectum and been expelled through the anus, thus 

 leaving a very wide and extensive rent between the rectum and 

 vagina. The mare is far more liable to this accident. because of 

 her spacious rectum, often filled with large, hard fecal masses, 

 and the tendency for the long and rigid feet of the foal or its 

 long and pointed nose to become displaced upward toward the 

 rectum, to be forced through the recto-vaginal wall. The mare 

 is further rendered liable to this injury because of the stormy 

 character of her labor pains and the rapidity of the passage of 

 the fetus through the birth canal. The rupture of the perineum 

 in this manner is therefore essentially an accident of the mare, 

 and is rarely, if ever, observed in other domestic animals. 



2. Rupture of the perineum may be caused in anj' animal by 

 overstretching of the parts as the result of forcing through the 

 birth canal a fetus of too large dimensions, and especially a fetus 

 with one or more extremities displaced, forming a projection and 



