UNIVERSITY OF CALIFORNIA PUBLICATIONS 
IN 
ZOOLOGY 
Vol. 9, No. 7, pp. 341-351 September 14, 1912 
OBSERVATIONS ON THE SUCKLING 
PERIOD IN THE GUINEA-PIG 
BY 
J. MARION READ 
While carrying on some experiments upon the period of ges- 
tation in the euinea-pig (Cavia cobaya) it beeame desirable to 
determine how long after birth the young are entirely dependent 
upon the mother’s milk for nourishment. 
It is a well-known fact that the young of this animal are 
born in a very mature state. The euinea-pig, quite in contrast 
to mice, rats and rabbits, comes into the world with the eyes 
open, incisor teeth well developed and a heavy coat of permanent 
fur. They are strong and able to run about at once. During 
the second or third day most young guinea-pigs begin to take 
solid nourishment. 
Abderhalden (1908, p. 371), in discussing the length of time 
that different animals require in which to double their weight 
after birth, says of guinea-pigs: “*Aecording to their develop- 
ment they scarcely belong in the ranks of mammalia; by eating 
green food shortly after birth they rapidly increase in weight. 
At birth they are already remarkably developed. Even then 
they are able to eat the same food as that of the mother... . 
The female of this animal possesses only two mammary olands, 
situated in the groin, and milk plays but a subordinate part 1m 
the nourishment of the new born guinea-pig.’’ 
G. Bunge (1902, p. 108), in considering the composition of 
the milk of this animal says: ‘‘From the first day of birth the 
