THE EFFECT OF AN ALBUMINOID DIET 411 



34.3 grams; calculating the amount of carbon in the food as 41.6 grams 

 daily, this would leave 7.3 grams retained. This carbon might be stored in 

 the form of glycogen or as fat. Calculated as glycogen, it gives an amount 

 greater than an animal of that size could retain. Therefore, the probabilities 

 are that the carbon is deposited in the form of fat. 



In the examination of the fat formed in the larvae of blow-flies developing 

 in a quantity of coagulated blood, Hoffmann found ten times more fat than 

 existed in the blood. These experiments point in the direction of fat for- 

 mation from proteid. 



The Effect of an Albuminoid Diet. The albuminoid eaten in great- 

 est quantity is gelatin. Though gelatin closely resembles the proteid mole- 

 cule chemically, it cannot replace the proteid of the food. In other words, 

 nitrogenous equilibrium cannot be maintained on a diet consisting of gelatin, 

 carbohydrates, and fats. Proteid food is absolutely essential to the reconstruc- 

 tion of the proteid molecule. Gelatin is one of the proteid-like substances 

 whose food value is comparable to that of carbohydrates and fats, as the 

 following experiments will prove : On a diet of 500 grams of meat, without any 

 gelatin, the subject lost nitrogen to the equivalent of 22 grams of proteid, but 

 when 200 grams of gelatin were added the subject gained 54 grams. In another 

 experiment, when the diet consisted of 2,000 grams of meat without gelatin, 

 the gain was the equivalent of 30 grams of proteid, but when 200 grams of 

 gelatin were added the gain became 376 grams. The lack of real proteid 

 food value is proven by still a third experiment in which the diet consisted 

 at first of 200 grams each of meat and of gelatin; here the gain was the equiva- 

 lent of 25 grams of proteid, but, when the meat was omitted and the gelatin 

 alone given, there was a loss of 118 grams. In these cases gelatin did not 

 take the place of proteid in any sense, but rather saved it from oxidation as 

 a source of energy. The proteid was so protected that, instead of being used 

 up, it helped to form tissue and increased the body weight. Gelatin, there- 

 fore, saves proteid material for constructive processes. 



Formation of Urea. The nitrogenous fraction of the proteid molecule 

 is in the end converted largely into urea and is excreted from the body in 

 that form, as described in the chapter on Excretion. The method of forma- 

 tion of urea, as well as the place where this occurs, has given rise to great 

 controversy, while the intermediate products between proteids and urea 

 have not as yet been fully determined. We can state with certainty that 

 urea is not formed in the kidneys, since it is not only found in the blood of 

 the renal artery, but it accumulates in the blood if the kidneys are diseased 

 or removed and the separation of the urine is interfered with. Circulation 

 of blood through the kidney does not result in the formation of more urea 

 than is present in the blood to begin with. 



There are a number of experiments that prove that urea is formed in the 

 liver. The power of the liver cells to form urea is shown by the increase of 



