3 io THE POPULAR SCIENCE MONTHLY. 



equivalent in the shape of fat (2, 4 : 1) ; consequently the sum must 

 have been 377 meat, 184 fat. The dry excrement was then only 20, 

 with five of fat. More albumen was, therefore, digested in the latter 

 case than in the former, for in the excretory residue from the bread 

 there was found of nitrogen 2.45, while in that from meat and fat it 

 was only 0.97. To show that it is really the starch which yields ex- 

 cessive residue, and not some other constitutent part of the bread, 

 Mr. Meyer gave the albumen of 1,000 parts of bread under the form 

 of pure flesh-meat, and also starch in the form of fecula reduced to a 

 pulp. The sum was 377 parts of meat and 522 of starch. This ration 

 yielded 68 parts of excrementitious matter per day, as when the 

 equivalent food was given in the shape of bread. Still these excreta 

 contained less nitrogen than that from bread. According to the 

 investigations made by Dr. Bischoff, more nitrogen was assimilated 

 out of 302 parts of meat and 354 of starch, than out of 800 of bread, 

 although in each case the quantity of albumen was equal. It is hence 

 seen that it is the starch which gives the greater part of the rejected 

 residue. It follows that carnivora and man living on vegetable food 

 ought to evacuate the bowels twice a day ; whereas, on an exclusive 

 meat-diet, they might retain the intestinal contents for at least four 

 days. 



Bischoff thinks that, as the starch must first be transformed into 

 sugar before it can be absorbed, there is not sufficient time for this 

 change to be thoroughly brought about, before the starch is carried 

 along by the general action of the intestine. At first, excrementary 

 matter has a very strong acid reaction, which, as Bischoff supposes, 

 is owing to the presence of a great quantity of organic acids, especially 

 butyric acid. Pettenkofer and Voit have found in the gases exhaled 

 by animals consuming starchy food, chiefly hydrogen and carburetted 

 hydrogen. These same gases are also found, in the intestine of the 

 herbivora. The expulsion of the starch is probably due to the gener- 

 ation of these gases, which excites the peristaltic movement of the 

 intestine. If the chyme were permitted to remain longer in the intes- 

 tine, the starch would be completely transformed into sugar and en- 

 tirely absorbed. The obstinate diarrhoeas of infants are doubtless often 

 occasioned by this same phenomenon. 



Voit shows that there are many other agencies which may exert 

 similar influence upon intestinal movement. His assistant, Dr. Hoff- 

 mann, has observed that when cellulose is added to human food, for in- 

 stance to flesh-meat, such meat then gives a largely-increased propor- 

 tion of excrementitious matter. Purgatives, or sudden refrigeration of 

 the abdominal region, may have the same effect. Bread containing all 

 the constitutents of wheat causes, according to Meyer's experiments, 

 prompt evacuation, by reason of the indigestible cellulose it contains. 

 It yields a widely disproportionate quantity of excreta, as has been 

 demonstrated by Panuni in the case of dogs fed on bread, wheD, 



