OJY THE DIGESTIBILITY OF FOODS. 311 



though evacuation increased, the amount of urea was diminished. 

 White wheaten bread gives least excreta. The proportion of water 

 contained in this matter affords the means of judging how long it had 

 remained in the intestine, and how far the process of extracting the 

 nutritive properties had gone. The substance evacuated in small 

 quantity after a meal of flesh-meat contains hardly any remains of 

 meat and 50 per cent, of solid matter, while the excreta from bread- 

 food, evacuated in greater quantity, with much of the bread not trans- 

 formed, has only 23 per cent, solid matter. 



It might be supposed that the yeast in the bread is the cause of 

 this ; but Meyer has shown that a ration of starch-pudding and un- 

 leavened bread gives residuum in equal proportion with leavened bread. 

 He has also shown that bread, into the composition of which enter 

 nutritive salts, according to the Horsford process, gives a residuum 

 equal to that of common bread. The result, therefore, is not due to 

 the absence of these salts from bread. Dr. Bischoff has shown, in the 

 course of some experiments he made at the instance of Liebig, that 

 the addition of extract of meat, with or without salt, to the bread 

 given to a dog, does not affect the intestinal absorption, nor does it 

 lessen the amount of excrementitious matter. The objection might 

 perhaps be urged that, as the dog is purely carnivorous, experiments 

 made on him will not warrant a universal conclusion. Therefore, Dr. 

 Hoffmann made the same experiment with a man. The man was fed 

 on potatoes, pulse, and bread, and there were then 116 parts of dry 

 excreta ; when extract of meat was added, there were still 109. 



According to Haubner, the addition of a little peas to potatoes 

 notably diminishes or even entirely dissipates the starch, which else 

 is found in great quantity in the excreta of sheep. This result he at- 

 tributes to the influence of the albumen in the peas. Dr. Bischoff 

 gave a dog 800 parts of bread and 100 of meat. The amount of residu- 

 um was not lessened, nor the assimilation of the bread increased. 

 Dr. Meyer found a dog, on 1,000 parts of bread, to give TO of excreta ; 

 on 1,000 of bread and 100 of meat, 66 parts ; and on 1,000 of bread 

 and 300 of meat, 75 of solid residue. There is, then, no means of pro- 

 moting the digestion of bread or potatoes, or other vegetable food, in 

 the intestine whether of man or of dog, nor of preventing the loss of 

 the starch. 



From the persevering observations of Dr. Hoffmann, it follows that 

 this imperfect digestion and this voluminous excretion are unavoid- 

 able a fact which, on a vegetable diet, necessitates larger consump- 

 tion, even though each of the elements were in itself capable of absorp- 

 tion. If a man consumes in a day 1,000 parts potatoes, 207 lentils, 40 

 bread and beer, he takes in 14.7 of nitrogen. Of the latter he gives 

 out 7 by the kidneys, and 6.9 in 116 of dry excreta. The latter con- 

 tain 24 per cent, of the dry food, and 47 per cent, of the nitrogen. 

 But, when he takes in animal food, the same amount of azote and oi 



