278 BULLETIN OF THE BUSSEY INSTITUTION. 
EXPERIMENTS WITH Rats. 
A few trials were made with rats in order to see whether the re- 
sults obtained in the experiments with mice were applicable to 
the rat as well. It was found that the rats when kept upon a 
rather short allowance of oats ate putty freely, and voided great 
cylinders of white dung. For example, a single rat of 134 grms. 
weight ate no putty when fed for a couple of days in June upon 
8 grms. of oats per day, but on putting a second rat into the cage 
and giving the two animals 4 grms. of oats and 20 grms. of putty 
(= 6 balls) they ate the whole of it, and the same result was 
obtained next day on repeating the last-named trial. Next day 
the animals were given 6 balls of putty made from a mixture of 
iy carbonate of baryta and 8; whiting, and 8 grms. of oats, and 
they ate only 3 of the balls. The same result was obtained on the 
day following with the same ration, although another small rat 
had been put in the cage. Next day the three rats received 6 
balls of putty made from a mixture of 1 carbonate of baryta and 
4 whiting, together with 8 grms. of oats, and no more than 4 of 
the balls were eaten. On the day following another large rat was 
added, and 6 balls of a mixture of equal parts of carbonate of 
baryta and whiting were put in the cage, together with 9 grms. of 
oats. Only one of these balls was eaten, but one of the rats was 
found dead. Finally several balls of putty made from pure car- 
bonate of baryta were given to the animals, and although none of 
them seemed to have been eaten,* another rat was found dead. 
The remaining rats were fed for several days with simple whiting- 
* In experimenting with rats it is difficult to tell how much of the offered 
material has really been eaten, since the restless animals tumble the balls 
about, trample them in the dirt of the cage, and crush them beyond recog- 
nition. 
Another difficulty encountered in experimenting both with rats and with 
mice is that when one of the animals dies, his body is soon eaten by the sur- 
vivors, who thus become gorged with food and indisposed to consume the ex- 
perimental rations. This craving for flesh is, however, no evidence that the 
animals were suffering acutely from hunger, for the same thing occurs con- 
stantly in ordinary life, where mice have no access to animal food. I have 
repeatedly seen the bodies of mice that had been strangled in a spring trap 
eaten off at the back of the head in the course of a few hours even in grana- 
ries and places where there was an abundance of vegetable food, and in places 
moreover where no rats where to be found. The fact does but enforce the 
wisdom of the popular notion that traps for rats and for mice should be baited 
with meat. 
