276 BULLETIN OF THE BUSSEY INSTITUTION. 
that the application of this idea would be beset with technical dif- 
ficulties ; but it might be studied nevertheless. 
During the foregoing trials with white-lead the mice continued 
to void light-colored dung, though the particles were not so large 
as those from whiting ; the color was moreover somewhat tarnished 
from the presence of a little black sulphide of lead. On analysis, 
this dung was found to contain an abundance of lead, and when 
dilute muriatic acid was poured upon the the dung enough sulphur- 
etted hydrogen was given off to react freely upon paper that had 
been moistened with acetate of lead. But no reaction for sulphur- 
etted hydrogen was obtained from dung that had been voided by 
the mice that were fed with whiting unmixed with white-lead. 
Carbonate of Zinc. A couple of mice accustomed to an allow- 
ance of 4 balls of plain putty per day were given 4 balls of putty 
made from a mixture of 1 part pure carbonate of zinc and 3 parts 
of whiting, and they ate them all. Next day they were given 4 
balls made from a mixture of equal parts of carbonate of zinc and 
whiting and they ate nearly all of them. On the following day, 
4 more balls of the half and half putty were given, and one of the 
mice was found dead. 
Oxide of Zinc. "Two mice were given several balls made from 
a mixture of 1 part pure oxide of zine and 3 parts whiting, and 
the balls were left in the cage during two days. Each day it could 
be seen that only a very small portion of the material had been 
eaten. But one of the mice died on the second day. A fresh 
mouse was put in the cage and the animals were fed with plain 
putty for three or four days, after which time they received each 
day, during three days, a couple of balls of putty made from a 
mixture of ;4; oxide of zinc and 59; whiting. One of the mice died 
on the third day. A fresh ball of the same mixture was given to 
the remaining mouse every day during five days, and almost every 
day he ate a part of it, sometimes almost the whole of it, but he 
suffered no apparent harm. He was next fed with plain whiting- 
putty for a day or two, and afterward again with putty made from 
mixtures of oxide of zinc and whiting as follows: During five days 
he got each day a fresh ball made from + oxide of zine and + 
whiting. Some days he ate very little of the mixture while on 
other days he ate a considerable portion of what was offered him ; 
meanwhile he remained lively and ate his oats with avidity. Every 
day during the next six days a couple of fresh balls of putty made 
