Extreme Variations in Size 271 



3. Violent Expulsive Efforts Following Coition. In the 

 mare and the cow we occasionally observe very violent expul- 

 sive efforts immediately following copulation. It is apparently 

 due, in some cases, to an irritability of the animal. If there has 

 been some pre-existing disease of the part, which has caused a 

 stricture of the coital canal, injury may follow the coition which 

 produces pain and is naturally accompanied by straining. We 

 observe the same results when the penis of the male is compara- 

 tively large and the copulation causes laceration or rupture of 

 the vagina. It is, consequently, most common in those cases 

 where the female is young or is of small size and the male is 

 large, and especially where the penis is of very large size or of ex- 

 cessive length. In other animals the expulsive efforts are ap- 

 parently due entirely to individual irritability. In such cases, 

 immediately following coition, there is severe straining, which 

 causes an immediate expulsion of a large part, or all, of the 

 semen and may result, according to Zschokke* and others, in 

 sterility. 



In all such cases, the cause of the irritation should be discov- 

 ered and removed. We have already suggested a plan for pre- 

 venting injury from the penis of the stallion under, ' ' The Dangers 

 and Infections of Coition ' ' on page 50. We have also pointed out 

 the danger of permitting copulation when the vagina is inflamed. 

 If the expulsive efforts are due to excessive irritability of the 

 animal they may be overcome or ameliorated by causing her to move 

 about constantly, or otherwise attracting her attention for some 

 time after copulation. 



IV. Extreme Variation in the Size of the Male and Female. 



Under " The Dangers and Infections of Coition," on page 50, 

 we have considered the question of the variation in the size of the 

 male and female with reference to accidents. Closely allied to 

 these accidents is the question of sterility due to this same lack of 

 correspondence in size. In all cases where accidents are liable 

 to occur because of this difference in size, sterility is likely to 

 result for similar reasons. If the female is comparatively either 

 too large or too small, sterility may ensue as a result of imperfect 

 or incomplete copulation. The nature of the cause suggests the 



*Zschokke, Die Unfruchtbarkeit des Rindes, page 137. 



