442 METABOLISM ON A DIET OF MEAT, ALBUMIN OR GELATIN. 



METABOLISM WITH AN EXCLUSIVE DIET OF MEAT, ALBUMIN 



OR GELATIN. 



According to Pfliiger the higher animal (as has been demonstrated experi- 

 mentally for the dog) can be nourished and maintained almost exclusively on 

 proteids, without impairment of its functional activity. Proteids are, therefore, 

 to be designated as foods of the first order, as fundamental foods. Pfliiger applies 

 the term nutritive requirement to the smallest amount of lean meat that is capable 

 of maintaining the metabolic equilibrium, without fat or carbohydrate of the body 

 being utilized for decomposition. The amount of this nutritive requirement is 

 determined by the weight of the flesh of the animal and increases with this on 

 addition of flesh to the body. The decomposition of proteids increases also with 

 the supply of proteid if the latter exceeds the nutritive requirement. Under such 

 circumstances, however, a certain portion of the excess of proteid is conserved 

 and deposited as flesh. The nutritive requirement of the dog is for i gram of 

 animal nitrogen 0.0636 gram of nutrient nitrogen; or i kilogram of nitrogenous 

 animal tissue requires 2.099 grams of nitrogen in the food. 



Human beings provided exclusively with meat free from fat are, however, 

 not able to maintain the metabolic equilibrium. Compelled to adhere to such a 

 diet permanently they would certainly succumb. The reason for this is obvious. 

 In beef the proportion of nitrogenous to non-nitrogenous elementary nutritive 

 constituents is as i to 1.7. The healthy person gives off daily in the carbon dioxid 

 of the respiration, in the feces and in the urine, about 280 grams of carbon. 

 If he desired to obtain these 280 grams of carbon from the carbon of an exclusively 

 meat-diet, he would be compelled to digest and assimilate more than 2 kilos of 

 pure meat in twenty-four hours. His organs, however, would by no means suffice 

 to accomplish this permanently. The man would under such conditions soon be 

 compelled to consume less meat. This result would require the decomposition of 

 the constituents of his own body, first of all the fat and then also the proteids. 



Also in the following manner it can be clearly shown that a human being is 

 unable to maintain himself on a meat-diet exclusively. A man weighing 70 kilo- 

 grams and doing a moderate amount of work requires 40,000 calories daily for each 

 kilo of body-weight, therefore a total of 2,800,000 calories. One thousand grams 

 of lean beef yield 95,000 calories. Such a person would, therefore, be compelled 

 to consume about 3 kilograms of beef, or 2,850,000 calories, daily, and this, natur- 

 ally, is impossible. 



The carnivora (dog) , whose digestive organs are especially adapted to the 

 digestion of meat, by reason of the short intestine and actively solvent in- 

 fluence of the digestive fluids upon proteids, cannot be maintained permanently on 

 chemically pure albumin, although this is possible with the leanest meat, which, 

 however, always contains not less than 0.59 per cent, of fat. Under such circum- 

 stances the animal consumes large amounts of meat, and as a result the elimina- 

 tion of urea is increased correspondingly. If it eat still larger amounts, it may 

 even put on flesh, and then, in accordance with the maintenance of the newly 

 deposited flesh, it requires naturally a constantly increasing amount of meat. 



The herbivora are under no circumstances capable of subsisting upon a meat- 

 diet exclusively, as their digestive apparatus, which is adapted for vegetable food, 

 would by no means suffice for the disposal of the necessary amounts of meat. 



Of gelatin it has been shown that it may replace the proteids in the food, 

 in so far as these serve as sources of energy and heat, but not if bodily tissue is 

 to be replaced. Under such circumstances two parts of gelatin take the place of 

 one part of proteid. The carnivora, which can maintain their metabolic equilib- 

 rium with large amounts of meat, are capable of doing this with less meat and 

 a corresponding addition of gelatin. According to Munk the dog is capable for 

 a few days of replacing of its proteid requirement by gelatin. A diet of gelatin 

 exclusively is, however, inadequate. In addition the animals soon lose their 

 appetite for such food. 



In consequence of its solubility the addition of gelatin (calf's-foot jelly) to 

 the food of convalescents has been recommended. The absorbed products of the 

 digestion of gelatin are conveyed to the connective tissues, which constitute a re- 

 pository for it. After a long-continued diet of chondrin, together with meat, 

 glucose has been found in the urine. 



