268 BULLETIN OF THE BUSSEY INSTITUTION. 
To prove that the mice ate the putty for the sake of the oil con- 
tained in it, special experiments were made in which lumps of 
solid chalk and balls of whiting made up with water, and of gyp- 
sum also, were offered to the mice, both at times previous and sub- 
sequent to those when the animals had been fed with putty. But 
none of these balls of chalk, whiting, or gypsum, free from oil, 
were ever eaten, no matter whether they were dry or moistened 
with water. At the most, marks of the animals’ teeth could some- 
times be detected on the whiting balls, but this was after the mice 
had become accustomed to eat putty and when they expected to 
receive a daily allowance of this substance. Sometimes the whiting 
and water balls, which were of course very friable, were found 
broken in pieces on the floor of the cage; but on collecting and 
weighing the fragments, the differences between their weights and 
the weights of the original balls was so small, that there was no 
reason to attribute the loss to any other source than mere mechani- 
cal waste, due to the adhering of some particles to the floor of the 
cage or to the cotton of the nest. Meanwhile the animals always 
began to discharge dark-colored dung on the third day after they 
had ceased to receive any putty. 
The great bulk and enormous quantity of dung discharged under 
the conditions above described, illustrates very emphatically the 
purgative or rather the evacuative power of coarse, indigestible 
foods. It recalls the remark of Liebig* that the boundaries of 
those German provinces in which the bran-bread, called pumper- 
nickel, is used may be traced by the remarkable size of the un- 
digested remains of the food of the inhabitants which wayfarers 
leave behind the walls and hedges. 
When the mice were eating putty freely, each separate piece 
or cylinder of their dung commonly measured a centimeter in 
length, —7. e. ten millimeters or nearly four-tenths of an inch, — 
and from 24 to 34 millimetres in thickness. Several cylinders were 
noticed that measured 12 mm. in length and 34 mm. in thickness 
colored, tenacious, fattish clay, which all kinds of cattle lick into great caves, 
pursuing the delicious vein. It is the common opinion of the inhabitants that 
this clay is impregnated with saline vapors, arising from fossil salts deep in 
the earth; but I could discover nothing saline in its taste, but I imagined an 
insipid sweetness. Horned cattle, horses, and deer are inordinately fond of 
it, insomuch that their excrement, which almost totally covers the earth to some 
distance round this place, appears to be perfect clay ; which, when dried by 
the sun and air, is almost as hard as brick.” 
* ** Familiar Letters on Chemistry,’’ London, 1851, p. 449. 
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