DIET OF ANIMALS. 193 



calf receives daily fifty-two grammes of inorganic matter in the milk 

 of the mother, and a calf six months old appropriates in its fodder 

 an amount of phosphoric acid corresponding to thirty-six grammes of 

 calcium phosphate ; while a horse fed on hay and oats receives daily 

 about one hundred and sixty-eight grammes of calcium phosphate. 

 Occasionally animals are seen to eat earth. This, with the exception in 

 the ease of birds, where gravel is required to assist in the comminution 

 of the food in the gizzard, is to be explained by the insufficiency of inor- 

 ganic matter in the food. Thus, the earth-eating Indians in South 

 America are said to consume earthy matters from the fact that their 

 corn is poor in salts. 



IV. THE DIET OF ANIMALS. 



The complexity of food-stuff's is essential to the sustenance of 

 the organism. The food must contain albuminoids for the recon- 

 struction of the tissues, carbo-hydrates and fats for calorification 

 and the formation of adipose tissue, and the saline matters for the 

 different secretions and tissues. If any one of these food-constit- 

 uents is not represented in the diet, the food, even although in 

 excessive amount, will be incapable of preserving health. Experi- 

 mentation has proved that single alimentary principles will not sustain 

 life. Magendie showed long ago that dogs fed exclusively on non- 

 nitrogenous substances, such as sugar, gum, olive oil or butter, in a short 

 time died of marasmus, the appetite soon being lost, ulcerations forming 

 on the cornea, and death occurring with all the symptoms of starvation 

 after about four weeks. After death all fat was found to have disappeared 

 from the bod}' ; the muscles were atrophied ; the urine alkaline and 

 .deprived of uric acid and phosphates, so as to resemble the urine of her- 

 bivora. Similar results were obtained whether the animals were fed with 

 oil, with gum, or with sugar alone. Any one' of these substances was 

 found to be incapable of sustaining life. Objection might naturally be 

 urged against these experiments that the dog being a carnivorous 

 animal, a diet of non-nitrogenous food was not adapted to his nutritive 

 needs ; but the repetition of Magendie's experiments by Tiedemann and 

 Gmelin with the goose, by feeding on gum arabic and water, sugar and 

 water, and raw or uncooked starch, overcomes the force of this argument. 

 In all cases death occurred in from two to three weeks with all the 

 symptoms of starvation, even though the examination of the excreta 

 proved that the substances given had been digested. In all cases the 

 appetite gradually failed, diarrhoea set in, and death occurred from 

 exhaustion and starvation. It thus seems clear that, even though 

 digested, a non-nitrogenous diet alone will not sustain life, either in the 

 carnivora or in the herbivora. A similar state of affairs holds for 



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