The Journal 
of Heredity 
THE ASS, LIKE THE ARAB, HAS ONLY FIVE LUMBAR VERTEBRAE 
The skeleton reproduced above is that of a hinny whose sire was a stallion with 24 vertebrae (6 
lumbar) and whose dam was a jenny 
with 23 vertebrae (5 lumbar). 
The fact that this hinny 
has only five lumbar vertebrae shows the tendency of the dam to dominate the anatomy of the foal 
in horses. (Fig. 20.) 
I am rather insistent on having the 
dorsal and lumbar vertebrae all 
counted, not only on account of this 
Arab specimen in variation from the 
true type but also because in the 
Museum of Natural History there is a 
skeleton of a wild horse of Asia, the 
Prejevalsky, and also one of a Kiang, 
each with 19 dorsal and five lumbar 
vertebrae, making the twenty-four. 
These are considered merely individual 
variations, the first lumbar having de- 
veloped ribs instead of the usual 
lateral flanges. A superficial observer 
might class them with the short back 
of the Arab because of the five lumbars. 
Similar individual variation has been 
found in a work horse and a Shetland 
pony, each with nineteen dorsals and 
six lumbars. Also a Grevy Zebra had 
eighteen dorsals and seven lumbars. 
SHORT BACK A RECESSIVE CHARACTER 
As the Thoroughbred, which is prac- 
tically all of Arab blood as his name 
indicates, never has the short back of 
the Arab, so far as I know, it seems 
evident that the short back is not a 
dominant character. (See Fig. 19.) I 
have found it to be dominant only in 
the first generation of outbreeding when 
the outbreeding is on the male side. 
That is a pure Arab mare bred to a 
trotting stallion produced a foal with 
five lumbar vertebrae (Museum of 
Natural History specimen). 
The weight carrying capacity of the 
ass has been known for all time and, 
he, like the Arab horse, has the short 
back of five lumbar vertebrae. 
A jenney or female ass bred to a 
stallion produced a-hinny which in- 
