4 FOREWORD 
In many instances the parasites and the host, when in 
health, get on very well together ; but when the host weak- 
ens the parasites may give him the finishing stroke. 
Though some morbid conditions described in this book 
are peculiar to capti\Tty, yet it seems reasonable to 
assume that many of the diseases found in captive ani- 
mals occur also in the wild. Some of the extinct races of 
animals may have been A\dped out by disease. 
Captivity causes numerous physical and mental dis- 
arrangements. Unaccustomed, unnatural and unvaried 
food, change of climate and environment, physical and 
mental degeneration from disuse of muscle and brain, 
fear, ennui, nostalgia, lack of the exhilaration of chasing 
and being chased, unsatisfied sexual feeling — all react 
harmfully on the captive. 
No captive animals get their natural food ; and though 
some, like the carnivora, may get approximately their 
natural food, yet they do not get it in the natural way. 
They have but little variety and may miss elements impor- 
tant to their well-being. They get only certain cuts — 
muscle and bone ; they do not get blood, guts and glands. 
The lion's meat is handed to him. He does not tear dowTi 
his prey ; and one result is that the jaws of the captive- 
bred lion differ decidedly in shape from the jaws of the 
w^ld-bred lion. He gets his food regularly, with awful 
monotony — twelve pounds of meat at 3.30 p.m. day after 
day; there is no alternation of feasts and fasts, with 
consequent change in the balance of the body reserves. 
Some animals, such as caribou, the moose, the black 
cock, the hoatzin, the koala, do not long survive captivity, 
because it is impracticable to obtain their natural food. 
Gastrointestinal disease is the commonest disease of 
wild animals. Twenty-five per cent, of sick humans in 
civilized communities also suffer from it. On the other 
hand, many animals become accustomed to the new diet 
and thrive on it. 
