CAUSES OF STERILITY IN THE MULE. 7 



CHARACTERISTICS OF THE MULE. 



The mule is a hybrid having for sire a jackass or male ass, 

 commonly termed a jack, and a mare for dam. If, however, a 

 stallion be bred to a she-ass which in the United States is called 

 a "jennet" and in England a jenny, the result is a hybrid known as 

 a hinny. It seems to be a well-established fact that no special 

 distinction with respect to appearance or conformation can be 

 made between mules and hinnies, because in both of these hy- 

 brids of both sexes the proportional resemblance to the horse and 

 ass is of infinite variety. Mares are generally taller than jennets, 

 hence the mules as a rule are of a greater height than hinnies, 

 which appears to be the only difference between these two hybrids. 



There seems to be a great deal of difference of opinion as to 

 which one of its parents the mule most resembles. For example, 

 Hayes ('04) says: "The coat, mane, tail, feet, and voice are more 

 or less intermediate between those of the horse and those of the 

 ass. The hind chestnuts in some cases are well developed, as 

 in the ordinary horse; in others, they are in a comparatively 

 vestigial form, and one or both may be absent. These hybrids 

 "resemble the ass more than the horse in their placid temper, 

 great adaptability to work, and longevity. In carrying or draw- 

 ing loads they are superior to horses of the same weight, and they 

 can obtain the necessary energy from food which horses cannot 

 digest, as for instance, the reeds on which the mules of the south 

 of France live. I have experimentally established the fact that 

 their digestive power is higher than that of horses" (Sanson). 



Lydekker ('12) says; "In the case of both mules and hinnies 

 the general build and appearance of the animal accord with the 

 type of the sire, although in the manner of bodily size the dam is 

 followed. Mules are therefore asinine in appearance, although 

 with a more horse-like tail, and relatively large ears; whereas, 

 the more horse-like hinny is small. If, however, females of the 

 great Poitou ass were to be utilized for hinny-breeding, the 

 progeny would probably be of larger stature. One exception to 

 the ass-like character of the mule is that it lacks the white belly 

 of its male parent." 



Wilcox ('07) says: "It is not true, however, as sometimes 

 asserted, that the mule eats less than the horse. On the contrary 



