Oct. 27, 1923 
Otocephaly in Guinea Pigs 
163 
HISTORY OF THE GUINEA PIGS 
The distribution of these otocephali by grade among the inbred families 
and other related experiments is shown in Table I. The inbred families 
have been maintained since 1906 wholly by matings of brother with 
sister except for Family 4, in which parent-offspring matings were the 
rule (75, 16). The foundation pairs of most of them (No. 1 to 24) were 
taken from a stock which had been maintained since 1894 by the Bureau 
of Animal Industry without the introduction of fresh blood. The females 
of Families 31 to 39 came from this stock, while the males were bought 
from a dealer. At present only five families (2, 13, 32, 35, and 39) are 
being maintained. 
Stock B represents the original stock, maintained with careful avoid¬ 
ance of matings closer than third cousins. Numerous crosses have been 
made among the families. 
In addition to the 82 octocephali shown in Table I and subsequent 
tables, there are records of two of unknown grade in an early experiment 
for which full data are not available. 
DISTRIBUTION AMONG INBRED FAMILIES 
The considerable number of otocephali which have appeared in the 
inbred families at first seems to support the old belief that inbreeding 
itself leads to the appearance of monsters. Further consideration, how¬ 
ever, throws doubt on this conclusion. We find that* 14 inbred families, 
with a total of 12,037 young, produced no otocephali at all, while 50 of 
the 82 appeared in one family, No. 13. This family produced 1.54 per 
cent, while only 0.11 per cent appeared in all other inbred families, taken 
collectively. 
Table I .—The number of otocephali of each grade among 24 inbred families, crosses 
involving these families, and a random-bred control stock, through June , IQ22 
Family No. 
Grades of otocephali. 
Total 
Total 
Per 
cent 
1 
2 
3 
4 
5 
6 
7 
8 
9 
! 10 
IZ 
oto¬ 
cephali. 
young. 
oto¬ 
cephali. 
4. 
I 
I 
I 
558 
I, 182 
0. 18 
2 
I 
2 
•25 
.09 
1. 54 
•15 
•23 
•93 
•33 
• 13 
.07 
. 00 
11. 
I 
0 
I 
I, 160 
13. 
2 
c 
6 
26 
2 
I 
I 
I 
2 
2 
I 
50 
2 
3.253 
1,308 
880 
17. 
I 
0 
I 
0 
18. 
1 
1 
2 
19. 
1 
■2 
I 
5 
Q 
537 
2, 718 
3 > 02 7 
1, 461 
12,037 
28,121 
32. 
2 
2 
O 
2 
I 
I 
■2C. 
O 
I 
I 
2 
y 
A 
26 . 
1 
I 
O 
14 other families. 
O 
Total inbreds. 
3 
1 
0 
0 
35 
0 
3 
1 
4 
2 
C 
3 
1 
4 
I 
78 
28 
.28 
Inbreds, excluding 
Family 13 . 
y 
4 
y 
•2 
2 
I 
0 
4 
1 
0 
24, 868 
6, 659 
4,495 
. 11 
Crosses. 
0 
y 
2 
1 
0 
2 
•05 
. 02 
Stock B . 
1 
O 
I 
Total . 
■2 
0 
0 
37 
4 
2 
e 
2 
4 
I 
82 
39 t 275 
. 21 
0 
y 
y 
0 
0 
.. 
60375—23 - 2 
