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 

 (H. 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 grcecoriim> 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. 



