THE EXCREMENTS OF MAN AND ANIMALS. 
277 
ethereal solution, allowed to evaporate spontaneously, was, after three days, found 
to contain a quantity of shining crystals, polarizing light under the microscope, and 
mixed with traces of a red amorphous deposit. The crystalline mass, dried first upon 
bibulous paper and then under the air-pump, assumed the form of slightly brick- 
coloured translucent scales. When heated upon a platina knife, they first fused, 
emitting the peculiar smell of the tiger’s den, and when allowed to cool exhibited 
a yellow waxy appearance, reflecting light powerfully under the microscope, but 
without any crystalline structure. They burnt with a bright flame, leaving traces 
of a white inorganic residue, probably from their not being quite pure, and hardly 
any black stain. 
The above substance is insoluble or very sparingly soluble in cold alcohol, but 
dissolved readily in that fluid when boiling. By concentrating the alcoholic solution 
on the water-bath, arborescent crystals were obtained which dissolved in cold ether, 
but not so readily as excretine, and again crystallized if the solution was allowed to 
evaporate spontaneously. These crystals are very similar to those obtained from the 
alcoholic solution, but appear to lose their structure more rapidly as the ether 
evaporates than they do when produced from the evaporation of alcohol. 
I am not disposed to consider the above substance, which appears to exist in the 
castings of all the carnivorous animals I have had an opportunity of examining, as 
identical with human excretine, which it resembles, however, in many of its proper- 
ties. It appears to differ from it, first, by the shape of its crystals ; secondly, by the 
smell it emits when burnt ; thirdly, by a much less degree of solubility in alcohol and 
ether. 
The filtrate from the lime precipitate was concentrated upon the water-bath, when 
a whitish-pink sediment was deposited, which, when examined under the microscope, 
was found entirely composed of small round crystalline masses radiating from a 
centre. The crystals, collected on a filter and dried, burnt on the platina knife with 
a bright fuliginous flame, and left a white residue, consisting of lime. This salt of 
lime was found to be soluble, though not very readily, in alcohol ; on adding a few 
drops of water to the solution it turned milky, and on cooiing the whole mass 
instantly crystallized. The addition of sulphuric acid immediately brought out a 
strong smell of butyric acid ; the salt obtained from this alcoholic extract was there- 
fore evidently butyrate of lime. It could not be the lactate, although its crystalline 
form is similar, as the lactate is exceedingly soluble in water, and can only be made 
to crystallize in a very concentrated solution, contrary to what took place with the 
substance obtained from the Tiger, which begins crystallizing long before the solution 
has attained a high degree of concentration. 
I was not able to ascertain whether butyric acid exists in the free state, or com- 
bined with a base, as an immediate principle of the castings of the Tiger. It is 
probable, considering the slight degree of acid reaction shown by the alcoholic 
extract, that this acid occurs in the form of a salt. 
