A REPUTED “GRADE MULE” 
The colt pictured in Fig. 6 is here shown at the age of one and one-half years. 
There is little 
visible evidence of the one-fourth ass blood which he is supposed to possess; but his owner 
says that his feet are mule-like, as are his actions. 
There are physiological reasons for 
doubting the accuracy of all stories of mules that breed, but many students have been 
willing to admit the fertile mule as a possibility. 
more like a mule than a horse. I have 
bred this mule again this spring and 
she only took the horse once. I think 
she will have another colt; if so I intend 
to start a breed of that kind.”’ 
PHYSIOLOGICAL STUDIES 
The ovaries of equine hybrids have 
not been frequently examined as have 
the testes. Ewart examined the ovaries 
of a zebra-horse hybrid of 10 years of 
age which had died. He found Graffian 
follicles present, one of them being 114 
inches in diameter. A ripe follicle in a 
16-hand mare is about 1%4 inches in 
diameter. ‘‘From the appearance of 
this follicle it might well have contained 
an almost ripe ovum.” This case has 
encouraged Prof. Ewart to say that 
“occasional fertility among female mules 
is not inconceivable.” Habenstreitt 
worked on the ovaries of a female mule 
and found follicles but no ova. Female 
mules exhibit regular periods of oes- 
(Fig. 7.) 
trum, but the exact seat of the cause 
of this cycle of changes is not clear. 
But despite this chain of direct and 
circumstantial evidence the body of 
scientists has always been sceptical, 
and even mule breeders themselves as a 
class are inclined to discredit reports of 
fertility among mules. 
The negative side of the question is 
stated boldly by Ayerault (91), who 
unhesitatingly asserts that all cases of 
supposed fertility are errors in observa- 
tion or recording. He says (p. 152) 
that “In Poitou, where 50,000 mares are 
annually used for mule production, 
fertile mules are unknown, although 
they are in the best possible 
condition to be fecundated,”’ since they 
are constantly pastured with stallions. 
In support of the negative side there 
are in general two lines of argument 
which are followed. 
1. All reported cases are cast aside 
as mere myth and anecdote, or as due to 
497 
