RESEARCHES ON PROTEID METABOLISM. 147 



that the urine passed on one day really represents that day's 

 nitrogenous excretion. The meat used for feeding the 

 dogs was the leanest that could be procured. A slaughterer 

 at Cologne had orders to telegraph to the professor at 

 Bonn whenever a particularly scraggy beast was to be 

 killed, and a servant was at once sent to get a sample of 

 the meat. The amount of fat in this sample was determined, 

 and, if the percentage was low enough, several hundred 

 pounds of the meat were purchased. This meat was finely 

 minced in a sausage-machine, so as to ensure uniform 

 composition, and then was packed in tin boxes, sealed and 

 sterilised. A sample of this meat was accurately analysed, 

 so that the exact composition of the food used in the ex- 

 periments was known, and the relation of nitrogen to 

 carbon had not to be guessed at, as in Voit's experiments. 

 I may here summarise Pfliiger's conclusions. 



1. A dog can live a perfectly normal life on a diet of 

 which the combustible constituents are nearly pure proteid. 



2. The smallest possible amount of proteid that must be 

 given to an animal to maintain its weight constant when no 

 fat or carbohydrate is given at the same time (Nahrungs- 

 bediirfniss) = 2*07 grms. N. per kilo, body-weight. 



3. The amount of food-proteid necessary is conditioned 

 solely by the amount of flesh on the animal, and is not 

 influenced by the fat or carbohydrate contained in the 

 animal. 



4. The disintegration of proteid increases pain passu with 

 the amount given in the food, a small quantity of the excess 

 being stored and adding to the weight of the animal. The 

 animal, however, cannot digest more than 30 to 40 percent, 

 in excess of the necessary amount of proteid. Therefore, 

 to fatten an animal, one must call into play all the digestive 

 mechanisms, i.e., use a mixed diet containing fats and 

 carbohydrates as well. 



5. If an animal receives an amount of proteid not 

 exceeding the necessary amount, increased administration 

 of fat or carbohydrate does not increase the metabolism, 

 but the whole excess is stored up as fat. As proteid has 

 no immediate influence on fat-formation, a fattening diet 



