348 University of California Publications in Zoology [Vou 9 
An attempt was made to wean the smaller animal (Ch) at 
seven days, but it returned to the mother. It was successfully 
weaned, however, at the end of nine days and suffered no ill 
effects therefrom. Its changes in weight are to be found in the 
third column of table IV. 
Per cent 
100 —— Weaned at 21 days 
ss Weaned at 9 days 
—-~ — Weaned at 7 days 
7 
80 5 ] oe 
| — ~~ Vet 
60- 
40- 
| 
20 
Lett 5 10 15 20 25 Days 
Fig. 2. Solid line shows the average growth of guinea-pigs weaned at 
twenty-one days, based on twenty-eight observations. The broken line 
shows the growth of Cb (2) weaned at nine days. The dotted line is the 
growth curve for Ca (Q) weaned at seven days. On all three lines the 
arrows mark the termination of the suckling period. Data taken from 
table 4, columns one, three and four. 
The next young one (Bb) experimented upon was taken from 
the mother when just six days old. It lost 5 grams the first day, 
but regained four by the end of the second day. Its weights are 
given in column five, table IV. The time required in which to 
