ZOOLOGICAL DISTRIBUTION OF DISEASE. 271 
cutaneous horn just commencing to protrude from it. 
The bird is interesting as illustrating the two modes 
by which these horns arise. The statement that birds 
have no sebaceous glands except the uropygial gland 
requires modification. 
Cutaneous horns, due to the hardening of secretion, 
occur as normal productions in several animals. Thus 
the patch of spines on the fore-arm of hapalemur 
(77. griseus) and on the fore-arm of the ring-tailed lemur 
(L. catta), are of this character. Even more curious are 
the wart-like processes formed on the skin of the thigh 
in lizards, from the hardening of the secretion furnished 
by the femoral glands ; this hardened secretion enables 
the male to clasp the female. 
Among the few diseases restricted to mankind must 
be mentioned leprosy. Elephantiasis grecorum, as true 
leprosy is called, is a very remarkable affection : it has 
never been seen in any animal other than man, although 
determined attempts have been made to communicate it 
to rabbits, monkeys, cats, dogs, and fowls. Neisser 
claims to have successfully produced leprous tubercles in 
rabbits and dogs, but the results have not been confirmed 
by others who have repeated his experiments. The 
latest contribution to this subject is by Dr. Beaven Rake, 
Superintendent of the Trinidad Leper Asylum. The 
possibility of causing leprosy by inoculation has occu- 
pied his attention during four years. He has performed 
fifty-four experiments, some being the direct introduction 
of the diseased tissues from man into the subcutaneous 
tissues of guinea-pigs and rabbits, and by feeding fowls 
on leprous material. In all cases the experiments failed 
to produce constitutional leprosy. 
