9 
1906-7.] Effect of Meat Diet on Fertility and Lactation. 
8*2. This difference would in all probability have been greater but for the 
fact that the average number of young suckled by the bread-and-milk 
animals was only 4 - 6, while that of the meat-fed animals was 6 3. 
As before stated, the longest period before the birth of the young 
during which the mother had been on a meat diet was thirty days. Taking 
this into consideration, the difference is sufficiently marked to point to the 
conclusion that the result of a meat diet is to diminish the amount of 
mammary tissue in nursing mothers. 
Table giving the Lactation History of Twelve Rats fed on an 
exclusive Bread-and-Milk Dietary. 
Weight of 
animal at 
death. 
Weight of 
mammae. 
Per cent. 
Time during 
lactation 
when killed. 
Number of 
young. 
Weight of 
young. 
grms. 
147 
grms. 
12-5 
8 
1st day 
7 
grms. 
32 
140 
10 
7T 
3rd day 
7 
45 
180 
18 
10 
6th day 
7 
70 
225 
18-5 
8*2 
10th day 
7 
115 
120 
17 
14-1 
21st day 
5 
150 
140 
19 
13*5 
21st day 
7 
220 
115 
7’5 
6*5 
21st day 
3 
120 
130 
11*5 
8-8 
22nd day 
4 
100 
160 
19 
11-2 
25th day 
7 
145 
160 
15 
9*3 
30th day 
6 
175 
0 
j 
13 
10 
... 
6 
150 
13-5 
9 
27th day 
Average percentage = 9’6. 
The effect of this relatively poor mammary development on the young 
of the meat-fed rats is shown by a comparison of their weights with those 
of the young of the control animals towards the end of the lactation period. 
Thus the average weight of each of the young of the meat rats at the 
twentieth to the twenty-first day is 21 6 grms., in contrast to 29 *4 grms., 
the average weight of each of the bread-and-milk young. It is thus 
evident that the young of the animals fed on meat suffer in genera 
