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ON THE CORNEOUS ADDITAMENTA OF ANIMALS. 8 March, 
The horn of the rhinoceros, differing in structure from that of 
every other animal, and placed in a situation, of which it is the only 
example, had long appeared to me to be an anomaly very deserving of 
examination ; and therefore on the present occasion, it was the first 
object of my curiosity and attention. The view which I now began 
to take, of its structure and nature, was afterwards, in the course of 
my journey, further confirmed by the following mode of reasoning, 
which, to render it less complicated, I shall confine to the class of 
Mammalia, or, as it is more commonly called, quadrupeds. Dispersed 
over the skin of all animals, are pores which I have supposed to 
secrete a peculiar fluid, which may be designated by the name of 
corneous matter. This secretion, or fluid, is designed by nature for the 
forming of various most useful and important additamenta, all of 
which, continue growing during the whole life ; have an insertion not 
deeper than the thickness of the skin ; and are further distinguished 
by the absence of all sensibility and vascular organization, being 
purely exuvial parts like the perfected feathers of birds. In all 
these parts, the growth takes place by the addition of new matter at 
their base. When these pores are separate, they produce hairs. 
When they are confluent and in a line, they produce the nails the 
claws and the hoofs, the fibrous appearance of which, naturally leads 
to the supposition of their being confluent hairs : and the same may 
be said of the scales of the Manis. The quills of the porcupine, 
hedgehog, and other animals, may be regarded as hairs of extra- 
ordinary size. When the pores are confluent and in a ring, they 
furnish the corneous case of the horns of animals of the ruminating 
class ; and when confluent on a circular area, they supply matter for 
the formation of a solid horn, such as we see on the rhinoceros. 
An examination of the structure and appearance of this latter, will 
be found to support my explanation of its nature ; as about its base, it 
is in most instances, evidently rough and fibrous like a worn-out 
brush. * It grows from the skin only, in the same manner as the 
* This appearance, has not escaped the notice of an eminent zoologist ; who says, 
that these animals " portent une corne solide adherente a la peau et de substance fibreuse 
