ON THE DIGESTIBILITY OF FOODS. 309 



of this essay of the learned Bavarian physiologist. As the subject 

 is important, we give a verbatim statement of the results. 



Vegetable food, it is well known, contains, as its essential nutri- 

 tive elements, albuminates, or nitrogenous materials, fatty matter, and 

 hydrates of carbon, with water and nutritive salts. Such food, there- 

 fore, has the same elements as animal food ; but in point of digesti- 

 bility the two differ widely. Thus, while the carnivorous animal, 

 when fed with sufficient flesh-meat, passes but little excrementitious 

 matter, while it traverses the entire intestinal tract within eighteen hours 

 after a meal ; the herbivorous animal, on the contrary, when fed abun- 

 dantly with vegetable substances, often retains the food in the intes- 

 tine a whole week ; and a considerable portion of this food remains un- 

 used. The proportion which the solid excretions bear to the weight 

 of the animal is, for a dog fed on meat, as 3 to 10,000; for man with 

 mixed food, 5 to 10,000 ; and for the ox, as 60 to 10,000. 



"We must observe that this difference is not due solely to the vary- 

 ing digestibility of the substances compared. These substances, as 

 found in the excreta of herbivorous animals, are not such as resist the 

 action of the digestive fluids. Henneberg and Stohmann have shown 

 that the proportion of such substances digested depends upon their 

 respective proportions in the sum of the food consumed. This is one 

 of the most important recent contributions to the physiology of diges- 

 tion. What renders vegetable food harder to digest is the fact that 

 the albuminoid substances, fatty matters, starch, etc., are there incased 

 in a coating of cellulose, to break up which requires some time. On 

 this account, the intestine of the herbivora is longer and more com- 

 plicated than that of the carnivora. The latter digest but a small pro- 

 portion of cellulose. The same holds good for man, except when he 

 consumes young cellulose but little consolidated, as tender pulse, roots, 

 or fruits. The cellulose of hay and grass is of such quality that the 

 human digestive apparatus cannot extract any of their nutritive ele- 

 ments. In order that we may utilize them, they must first be trans- 

 formed by herbivora into their own substance. 



Albuminates, whether derived from the animal or from the vege- 

 table kingdom, leave but little alimentary residue. If fat be added to 

 the albuminates, this residue is increased in proportion to the amount 

 of fatty matter, especially when the latter is in excess. The addition 

 of sugar, no matter in what quantity, has not the same result, provided 

 it does not cause a diarrhoea. Of sugar, but faint traces are to be 

 found in the residuum. With starch it is quite different, even when 

 it is made pulp by boiling. 



Adolph Meyer has made some interesting experiments in this 

 matter. A dog was given 1,000 parts of bread per day (536 dry mat- 

 ter) and with such food his excreta amounted to 70 parts of dry sub- 

 stance. The equivalent of the albumen in the bread was then given, 

 in the shape of flesh-meat, its starch being replaced by the respiratory 



