BULLETIN OF THE BUSSEY INSTITUTION. 273 
able quantity of the mixture was consumed. But considerable 
quantities of mixtures of clay and whiting were eaten, as will 
appear below. The first trial of such mixtures was made with 6 
balls that contained, beside oil, 1 part of clay to 3 parts of whiting, 
and 4 of the balls were eaten. On repeating the trial next day 
with 3 fresh balls of the mixture all of them were eaten. Next 
day 6 balls made from equal parts by weight of clay and. whiting 
were offered and 4 of them were eaten, and on the day following 
4 fresh balls of the same mixture were eaten well-nigh completely. 
Four balls were then given made from 3 clay and 4 whiting, and 
3 of them were eaten in the course of the day. Finally, putty 
made from clay alone was again offered, and it remained prac- 
tically uneaten, as at first; though one of the balls was much 
broken, and tooth-marks were visible on several of the balls. The 
dung produced during the trials with clay was grayish-white and 
in much shorter cylinders than that resulting from whiting alone, 
as if there were greater difficulty in its passing through the 
animals. } 
Carbonate of Baryta.* Three mice which had been fed for 
several weeks with putty were given some pure, soft (precipitated) 
carbonate of baryta made up into balls with oil. Next morning 
two of the mice were found dead, though only a small quantity of 
the barium compound had been eaten from one of the balls. The 
rest of the material was immediately removed from the cage and 
the other mouse was fed upon oats alone until it was plain that he 
* Carbonate of baryta was employed many years ago in England as a rat 
poison; and it would doubtless be of convenient use in some cases, such, for 
example, as the preventing of mice from girdling trees. But, as will be seen 
in the text, the barium compound needs to be pure in order to be efficacious. 
Since this note was written, Professor Crampe of the Agricultural School 
at Proskau, in Silesia, has published the results of a series of experiments 
which were made by him to test the comparative activity of the various poi- 
sons most commonly employed for destroying rats and mice. He finds that 
the most effective of all is precipitated carbonate of baryta mixed to a thick 
paste with three times its weight of barley meal, and with water, and rolled 
into little pills. 
Crampe found that while neither fowls nor pigeons ate this paste, rabbits 
did eat it and were poisoned by it. Hence it may possibly be true that in 
some cases the mixture of carbonate of barium and oil, such as was used in 
my experiments, may be exhibited to better advantage than Professor Crampe’s 
paste. The latter is probably of more general applicability than the putty, 
but perhaps rather less safe in some instances? 
