Chemistry and Physics. 



67 



1. 2. 3. 4. 



Albumin 5690 10991 4857 9381 



Blood fibrin 5532 10820 4586 8970 



Muscular flesh 5731 10671 4749 8841 



Haemoglobin .5915 10617 4964 8902 



Casein 5629 11080 4799 9580 



Ossein 5414 10806 4544 8976 



Chondrin (calf) 5346 10544 4506 8924 



Vitellin 5784 11166 4954 8596 



Yolkof egg 8124 12052 7704 11632 



Vegetable fibrin 5836 10807 4986 9047 



Crude gluten 5995 10878 5245 9338 



Isinglass 5242 10800 4192 8640 



Fibroin 5097 10599 4077 8479 



Wool 5567 11099 4537 9009 



Chitin 4655 9943 4235 9043 



Tunicin 4163 9014 4063 8794 



In a second table given in the memoir, the percentage composi- 

 tion of these substances is given. It appears from the data given, 

 therefore, that the average heat of combustion of the food-albu- 

 minoids is about 5691 calories per gram, or 10870 calories for the 

 quantity which contains one gram of carbon. The loss of heat 

 resulting from the elimination of nitrogen in the form of urea is 

 16 per cent. The mean heat of combustion of the carbohydrates 

 is 9470 calories for the quantity containing one gram of carbon, 

 the heat for one gram varying with the hydration. This heat is 

 about one-fifth greater than that of the carbon present, this 

 reserve of energy being the source of the heat developed during 

 many fermentations. In the case of fats the heat of combustion 

 per gram of carbon is from 12200 to 12500 calories owing to their 

 small percentage of oxygen. About one-sixth of the total possi- 

 ble heat of the albuminoids is not available since the nitrogen is 

 eliminated as urea ; but in the fats and carbohydrates all the heat 

 of combustion is available. 



In another paper, Berthelot and Andre have given the heat of 

 combustion for several nitrogenous compounds derived from the 

 albuminoids; this heat being determined by combustion in oxy- 

 gen in the calorimetric bomb. Glycollamine yields 3133*6 calor- 

 ies per gram, alanine 4370*7, leucine 6526*1, asparagine 3396*8, 

 aspartic acid 2911*1, tyrosine 5915*9, and hippuric acid 5659*3. 

 If the total heat of combustion be compared with the heat of 

 combustion when the nitrogen is eliminated in the form of urea- 

 conditions closely resembling those of the living organism — it 

 will be observed that the heat is very much less in the second 

 case; indicating the important part played by urea in connection 

 with animal heat. If the nitrogen is eliminated in the form of 

 uric acid, the deficit is 115200 calories per 14 grams, or 122000 

 calories if the carbon dioxide is in solution. If the nitrogen is 

 eliminated as hippuric acid the deficit per 14 grams is 1012900 

 calories. In the herbivora, compensation occurs in the liberation 

 of free nitrogen in the intestines and so the thermal deficit is 

 small.— C. JR., ex, 884, 925; J. Chem. JSoc, lviii, 936, 937, Sep- 

 tember, 1890. G. F. B. 



