CHEMICAL SCIENCE. 207 



another important change took place in the stomach, namely, the de- 

 composition of the neutral fats and setting free of the fatty acids ; this 

 was an important decomposition, for the bile would form an emulsion 

 with a fatty acid, but not with a neutral fat ; some of the fat sometimes 

 escaped decomposition, but the pancreatic secretion formed an emulsion 

 with this portion. The formation of an emulsion seemed to depend on 

 the incrustation of each globule with a layer of soap, which prevented 

 the globules from coalescing, and increased their specific gravity, so 

 that they remained for a long time suspended in the liquid. Dr. Mar- 

 cet considered that in experiments on digestion it was always better to 

 employ gastric juice obtained directly from the stomach of an animal, 

 instead of an artificial compound, such as was employed by some physi- 

 ologists. There was some dispute as to the nature of the free acid ex- 

 isting in the gastric juice, some supposed it consisted of hydrochloric 

 acid, while others imagined that other free acids, especially lactic acids, 

 were present ; since quantitative determinations of the amount of hy- 

 drochloric acid and of the bases present in the gastric juice showed 

 that there was more hydrochloric acid than was sufficient to combine 

 with all the base, it was evident that there must be some free hydro- 

 chloric acid present ; it was highly probable, however, that other acids 

 were present in a free state ; for on placing some gastric juice in a 

 dialyzer and leaving it until all the hydrochloric acid had passed away, 

 the remaining matter was found to be still acid. It had been supposed 

 that the soda introduced in the shape of common salt with the hydro- 

 chloric acid of the gastric juice was employed in the formation of bile ; 

 but it appeared from, the interesting researches of Dr. Bence Jones 

 that this was not exactly the case, for healthy blood was always alka- 

 line, but appeared to have an incessant tendency to become acid ; the 

 acid was, however, as rapidly removed by the secreting organs ; and it 

 had been found that when the secretion of gastric juice was active, the 

 urine became less acid, and it gradually increased in acidity as the 

 gastric secretion was moderated, so that the two actions balanced one 

 another. It appeared that if no salt were supplied with the food eaten, 

 the hydrochloric acid secreted was totally absorbed again with the 

 food, furnishing an example of that wonderful power of adaptation to 

 circumstances which enabled animal life to continue under varying 

 external conditions. The only materials of the food that passed through 

 the stomach and intestines undigested were such substances as hair, 

 horns, etc. ; together with these, however, a small quantity of excre- 

 mentitious matter, obtained from the various secretions poured into the 

 intestines, was always present, and a crystalline matter of definite 

 chemical composition, and bearing some analogy to cholesterine, might 

 be extracted from it. 



LIEBIG'S THEORY OF FOOD. 



After having for many years enjoyed an almost uncontested appro- 

 val from physiologists and chemists after having been the universal 

 doctrine taught in class-rooms and text-books and after having been 

 put to the test by cattle-breeders Liebig's theory of food is now be- 

 coming less and less accepted among real investigators ; that is to say, 

 among men who, loyal to fact, are able to resist the seduction of a fa- 

 cile formula which seems to explain the mystery, but really leaves it 



