Another illustration of how modifications of the diet which formerly would have seemed unimportant, may make a difference between failure and success in growth and development is afforded in the experience of those who have attempted to rear young carnivora in captivity. It was not possible until within recent years to rear young lions in zoos or circuses, but to-day this is being done successfully in several places. Formerly it was the custom to give lions a large bone with a quantity of muscle attached. The animals ate the muscle tissue and attempted to gnaw the bone, but this was too large and hard to permit them to secure much of its substance. There was danger of choking on bones which might be splintered, or which could not be cracked, yet which were so large as to be swallowed with difficulty. They were, in other words, restricted too largely to muscle meat and to an inadequate amount of bone substance. Under these conditions young lions invariably developed rickets and had to be killed because they were so deformed as to be unfit for exhibition. Now it has been learned that the diet should consist of liver and other glandular organs, such bones as shoulder blades which are easily consumed, fat, and at intervals of a few days pigeons or rabbits, the entire carcasses of which can be eaten. Muscle tissue is fed rather sparingly. Under such management, it is easily possible to secure satisfactory nutrition in these animals. The reason why such a practice succeeds where the older one failed, is now understood in the light of our knowledge of the special dietary properties of each of the tissues of the animal body.

431. The Carnivorous Diet May Be Highly Satisfactory

It will be readily appreciated from what has been said, that both in human and animal experience, the carnivorous diet, when properly selected, of the diet which is largely carnivorous but supplemented with moderate amounts of vegetable foods, may prove highly satisfactory for the promotion of growth and the maintenance of vigor and longevity.

432. The Oriental Diet

We may next consider a type of diet which has served to nourish more than half of the human race from time immemorial, and is still depended upon by more than half of mankind. This type is that used so extensively in China, Japan, the Philippines and elsewhere in the Orient. In it the vegetative parts of plants, the leaves, form a very prominent part of the food supply.