206 ANNUAL OP SCIENTIFIC DISCOVERY. 



i 



by experience the difference in nutritious effect produced by the flesh 

 of tired cattle on a march, and those slain in a condition arising from 

 abundant food and healthy exercise. In a former case any amount 

 might be eaten without the satisfaction of hunger, whilst in the latter 

 a smaller amount removed hunger. But I discovered that certain other 

 food of a different quality, such as grape-sugar and fruit, would help the 

 tired meat to assimilate, and thus to remove hunger." Puddings and 

 fruit-tarts are not, therefore, simply flatteries of the palate, but digest- 

 ive agents ; provided, always, they are not themselues made of rebel- 

 liously indigestible materials. The reviewer alludes to the fondness of 

 artisans for confectionery, and of patients just discharged from the hos- 

 pital asking for " sweets " in preference to " good substantial food," as 

 examples of a correct instinct. There is no doubt that in children, in 

 whom the requirements of growth call for a rapid and efficient trans- 

 formation of ibod into tissue, the demand for sweets is very imperious ; 

 and parents should understand that the jampot will diminish the butch- 

 er's bill, and increase the amount of nutrition extracted from beef and 

 mutton. 



THE CHEMISTRY OF DIGESTION, BY DR. MARCET. 



Until very recently, but little attention had been bestowed by 

 chemists on those changes which go on under the influence of organic life, 

 and, in consequence, many vague speculations had been entertained 

 and published concerning this most interesting department of science ; 

 of late years, however, many able investigators had taken the subject 

 in hand, and much progress had already been made. Many obstacles 

 attended these inquiries, on account of the difficulty of observing the 

 conditions of the immediate principles during life ; the term " imme- 

 diate principles " being applied to those substances produced by organ- 

 ic life from which no less complex body could be obtained without a 

 complete destruction of the substance in question. As an example of 

 the power possessed by organic substances of preventing ordinary 

 chemical reactions, the influence of albumen or the serum of blood on 

 lactate of iron was shown. A mixture of this salt with white of egg 

 gave no color with ferrocyanide of potassium, although the lactate 

 itself furnished the ordinary blue precipitate. With respect more es- 

 pecially to the chemistry of digestion, it appeared that after a long fast, 

 the contents of the stomach were alkaline, and very small in quantity ; 

 as soon, however, as food was introduced, the gastric juice was secreted 

 in quantity, and an acid reaction was perceptible. The object of the 

 action of the gastric juice was, no doubt, to render the food capable of 

 absorption ; and accordingly it was found that albuminous, gelatinous, 

 and other similar matters introduced into the stomach, became convert- 

 ed into a substance called " peptone," which, according to Lehmann, 

 might be viewed as the same body, whatever nitrogenous food was 

 employed ; it had been shown, however, that the peptones resulting 

 from the digestion of cartilage and the mucous membranes rotated the 

 plane of polarization of light, whereas peptones from albumen had not 

 this power. The gastric juice, which was at first abundant, gradually 

 diminished in quantity and became more acid, probably in order that 

 it might act on the less masticated or less easily digestible portions of the 

 food. Besides the conversion of the albuminous matter into peptone, 



