402 POPULAR SCIENCE MONTHLY. 



insisted that they should come with empty stomachs, and then 

 sent them home as hungry as wolves. About this time he also 

 succeeded in demonstrating that frogs exhale more carbonic acid 

 in the light than in the dark, thus proving that light accelerates 

 the processes of assimilation in animal organisms, and that, too, 

 independently of the temperature of the environment or the 

 motion of the animal. 



Meanwhile he had prepared and published his Lelire der 

 Nalirungsmittel (Erlangen: Enke, 1850). This work, of less than 

 two hundred and fifty pages, written " fiir das Volk," and admira- 

 bly adapted to convey popular information concerning the diges- 

 tive qualities and nutritive properties of common articles of food, 

 was favorably received, and in a few years passed through three 

 editions. It presented in a clear and concise manner the results 

 of researches embodied in his Physiologie der Nahrungsraittel, 

 issued a few months earlier and intended for physicians and nat- 

 uralists, and was translated into Dutch, English, French, Italian, 

 Spanish, and Russian. It is divided into three principal parts, 

 the first of which treats of the general metamorphosis of matter 

 in living organisms, the origin and formation of the blood and of 

 the solids in the human body, the processes of assimilation, segre- 

 gation, and excretion as the conditions of growth, and the physio- 

 logical nature of hunger and thirst as sensations which inform 

 the brain through the medium of the nerves that the blood is 

 being impoverished. In the second part he shows how this impov- 

 erishment is checked and the waste repaired by nutriment, of 

 which the various kinds — meat, eggs, bread, cake, peas, beans, len- 

 tils, potatoes, beets, cabbage, and other vegetables, and different 

 sorts of fruit — are discussed as to their alimentary functions and 

 value. We then have a chapter on drinks — water, milk, tea, cof- 

 fee, chocolate, beer, wine, and brandy — and another on spices, or 

 rather on condiments, in which are included not only salt, pep- 

 per, mustard, ginger, and other spices, but also butter, olive oil, 

 vinegar, sugar, and cheese. In the third part there are rules of 

 diet in their application to man as a not strictly omnivorous, but 

 largely multivorous microcosm, with remarks on breakfast, din- 

 ner, and supper, nutriment for infancy, youth, middle life, and 

 old age, for women, workmen, artists, scholars, and other persons 

 of sedentary habits, and the different sorts of food suitable for 

 summer and winter. All these points are discussed in a series of 

 short sections with a perspicacity and perspicuity and power of 

 condensation rarely combined in scientific treatises. This feature 

 of the work was especially praised by Alexander von Humboldt. 



Perhaps even a greater sensation than by the book itself was 

 made by a long review of it in a Leipsic weekly journal {Blatter 

 fiir literarische Unterhaltung, November 9, 1850), by Ludwig 



