Mar. 20, 1916 
Inheritance of Fertility in Swine 
1147 
fat and an adipose degeneration of the sex glands. Whether these are 
really causes of decreased fertility is doubtful, since the best evidence 
shows them to be symptoms of reproductive derangement. 
Overfatness occurs frequently as a result of disturbances in the metab¬ 
olism, due to loss of secretion from several of the ductless glands, the 
sex gland being here included. Castrating or spaying are known to pro¬ 
mote obesity; hence, it is quite reasonable to assume that if testicular or 
ovarian derangement first occurs, then fat deposition will follow. Over¬ 
fatness would thus merely indicate and not initiate reduced fecundity. 
Market hog raisers usually believe that pure-bred hogs are deteriorating 
in prolificacy, in line with the common idea that inbreeding ultimately 
results in barrenness. Bitting, in 1898 (1), investigated the average 
size of the first 200 litters and the last 200 litters recorded at that time 
in the herdbooks of the Berkshire, Ohio Poland-China, Standard Poland- 
China, and Improved Chester White registry associations and found 
that during the period in which registration had taken place the Berk- 
shires had decreased 0.19 pig per litter, the Poland-China had increased 
0.225 and the Chester White had increased 0.1 pig. Rommel (22) 
investigated the same point for a period of 20 years in books of the Ameri¬ 
can and Ohio Poland-China associations, comparing the average size 
of litter for the first 5 years with the average for the last 5. The in¬ 
crease was 0.62 pig per litter among the American Poland-Chinas and 
0.43 pig per litter in the Ohio strain. A similar study by Rommel (22) 
on the Duroc-Jersey covering over 15 years showed an increase of 0.57 
pig. The changes which have occurred here are manifestly opposed to 
the idea that purity of blood lines diminishes fertility. On the other hand, 
the purity of blood can not be credited with the increase, since a constant 
selection for large litters has taken place, although an increased homo¬ 
zygosis for prolificacy might come about gradually with years of such 
mass selection as ordinary stock breeding involves. 
Hammond (8) has shown that ova may be lost either before or after 
fertilization; and, still more important, he has discovered that a relatively 
high percentage may atrophy during the earlier stages of embryonic 
growth. Lewis (9) indicated that there may be morphological interfer¬ 
ences with reproduction, so that fertility may be decreased. He found 
that the sperm cells of the boar are practically all dead after being in 
the uterus for 48 hours, which would, of course, result in a reduced 
fertility. Lewis’s results on the viability of sperm differ from those of 
Diihrssen (11), who observed living sperms in the Fallopian tubes of a 
woman patient three weeks after copulation had taken place. The 
importance of this question is probably confined to individual cases. 
Certain relatively extraneous characters are popularly supposed to be 
correlated with high fertility. Many farmers believe that “big type” 
or “cold blooded” hogs farrow larger litters than “hot blooded,” or 
