274 EVOLUTION AND DISEASE. 
seen that the form of idiocy known as cretinism is— 
recognized in calves, dogs, and lambs. Horses are cer- 
tainly known to suffer attacks of acute mania, and dogs © 
become demented and are occasionally imbecile, not — 
recognizing their master from other persons, and forgetting 
their own names. From being keen at sport, they fail to — 
recognize a hare or partridge, even blunder over them in 
a field and take no notice of the game when it rises. 
Convulsions caused by troubles during dentition are well — 
recognized in dogs, as well as a nerve affection, closely 
similar to epilepsy. The remarkable affection of human — 
beings termed locomotor ataxy, and the singular St. 
Vitus’ dance, or chorea, occur in dogs. 
It will, perhaps, be desirable to conclude this chapter 
by a brief consideration of the strange disease known as 
Elephantiasis arabum, the zoological and geographical 
distribution of which is limited in an interesting manner 
by mosquitoes. 
In India, China, Egypt, Arabia, the West Indies, and 
Australia this disease is endemic: it is characterized by 
enlargement of the parts affected, which may be the 
arms, legs, and other parts of the body. The skin cover- 
ing the part becomes enormously thickened, forms hard 
masses and folds obscuring the toes when the legs are 
affected, producing an appearance not unlike an 
elephant’s leg. One of the most remarkable features in 
this extraordinary disease is that very frequently the 
blood of individuals with elephantiasis swarms with 
minute hematozoa, named by Lewis /i/aria sanguinis 
hominis ; and recent researches go to show that the 
presence of filaria in the blood in association with 
