Page:Popular Science Monthly Volume 1.djvu/322

310 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 excessive residue, and not some other constituent 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 [sic] 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 generation of these gases, which excites the peristaltic movement of the intestine. If the chyme [sic] were permitted to remain longer in the intestine, the starch would be completely transformed into sugar and entirely 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. Hoffmann, has observed that when cellulose is added to human food, for instance to flesh-meat, such meat then gives a largely-increased proportion of excrementitious matter. Purgatives, or sudden refrigeration of the abdominal region, may have the same effect. Bread containing all the constituents 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, when,