THE HAIR AND FUR OF ANIMALS. 
107 
had been strong, as in the rat, or mouse, in these re- 
treats for life it would have doubly retarded the progress 
of the creature ; first by its resistance, and then acting 
as a brush, so as to choke up the galleries, by removing 
the loose earth from the sides and ceilings of the arched 
ways ; thus impeding at least, if not absolutely prevent- 
ing, retreat ; but the softness of the fur obviates both 
these fatal effects. 
The construction of the hair and fur of different 
creatures is very various and beautiful ; and if we be- 
lieve in the beneficence of the All-wise Creator, we 
must conclude that such peculiar fabrications were re- 
sorted to for the purpose of being immediately useful, 
or as necessary to the condition of the animal. In a 
mere sketch like this, it would conduct me infinitely 
beyond my intentions, to enumerate the many varieties 
of hair that are rendered manifest by the microscope ; 
but three or four may be mentioned. The fur or clothing 
of the mole is internally composed of collateral bars. 
In man the hairs have at times a central tube, for the 
conveyance of medullary matter, as in bones, or some 
nutriment analogous to it ; but in the mole there appears 
to be no communication with the body of the animal, 
unless the perspirable matter is conducted alternately 
from side to side along the bars. The fur of the bat 
has knots like the rudiments of branches. The hairs of 
the hamster mouse have a central perforation, appa- 
rently uninterrupted throughout their whole length. 
Some of the caterpillars (callimorpha caja) have spines 
proceeding from the hair that invests their bodies,* 
All these, and the other various contrivances so manifest 
in the coverings of animals, are probably designed to con- 
vey off the perspirable fluids conducive to health in an 
* The organ, which inflicts the pain, or sting, when we incautiously 
handle the nettle, is well known to be connected with a little vessel 
containing an acrid fluid, which being compressed, rushes up the tube 
of the organ, and is thus conveyed into the wound ; and it is rather 
singular, that the larvse of the admirable butterfly, which feeds upon 
the large hedge nettle, has the spines which arise from its body 
branched, and each collateral hair arises from a little bulb, similar to 
that of the plant on which it is chiefly found. 
