oO 
— 
1912] Read: Suckling Period in the Guinea-Pig a 
get some fat from the solid food which supples all the fat the 
adults require, we are led to believe that the young require more 
fat in proportion to their size than do adults. The reason for 
this greater need of fat we see when we consider the high heat- 
value of this food. The loss of heat by radiation from the body 
of a small animal is greater in proportion than that from the 
body of a larger one, hence more fat is needed to make good the 
loss. The high content of fat and low content of the other con- 
stituents of the milk indicate that the young guinea-pig is fitted 
to subsist upon other food than milk. That the young begin to 
eat solid food very early is shown by the observed fact that an 
animal ate hay when eighteen hours old. 
The post-natal retardation of growth characteristic of ‘‘all 
mammals so far studied’’ is but very slight in the case of the 
guinea-pig. 
In view of the facts set forth in this paper the following 
conclusions seem justifiable : 
1. A guinea-pig can be successfully weaned as early as the 
fourth day. 
2. Providing that the animal is healthy, its size and weight 
have httle or nothing to do with the result in early weaning. 
3. The percentage of weight lost the first day by the young 
(previously considered) guinea-pigs weaned before the usual time 
bears an inverse ratio to the age of the animals at the time of 
weaning. 
Transmitted April 24, 1912. 
ZOOLOGICAL LABORATORY, 
UNIVERSITY OF CALIFORNIA, BERKELEY. 
LITERATURE CITED 
ABERHALDEN, E. 
1908. Text-book of physiological chemistry (New York, Wiley), xiii 
-+ 722 pp., 3 figs. in text. 
BUNGE, G. 
1902. Physiologie and pathologie chemistry (Philadelphia, Blakiston), 
2nd English ed., trans. from 4th German, viii + 470 pp. 
Minor, C. S. 
1891. Senescence and rejuvenation, Journ. Physiol., 12, 97-153 pls. 
1-4. 
