94 CHEMICAL COMPOSITION OF THE BODY. 



suspected liquid, when, if either of the biliary acids be present, the fluid 

 assumes a bright cherry color, which gradually deepens to purple. Nothing 

 is accurately known respecting the origin of the biliary substances just 

 noticed; part is probably preformed in the blood, and is only filtered off by 

 the liver, but part, there can be little doubt, is formed in the liver, and re- 

 sults from the decomposition of albuminous and oleaginous compounds. 



55. HYDRO-CARBONACEOUS COMPOUNDS. The uon-azotized or hydrocar- 

 bonaceous organic compounds which enter into the composition of the body 

 may be divided into two groups, the saccharine and the oleaginous. The 

 principal saccharine substances are milk and grape sugar, iuosite, glycogen, 

 and the acids resulting from their fermentation. The chief oleaginous com- 

 pounds are olein, stearin, palmitiu, and cholesterin. Both the oily and the 

 saccharine groups are of great importance in the processes of nutrition and 

 development, and are scarcely ever absent either in the food, the blood, or the 

 tissues. There can be little question that the saccharine compounds con- 

 tained in the body are partly derived from the farinaceous and saccharine, 

 and partly from the decomposition of the albuminous compounds, the latter 

 process occurring especially in the liver. That a great part of the saccharine 

 and amyloid compounds is derived directly from the food is clearly shown 

 by the following experiment of M. Bernard. 1 The muscular tissue of a 

 fasting horse was found on careful examination to be perfectly free from 

 amyloid substances; but in the muscles of the same animal, a few hours 

 after a full meal, clear evidence of their presence was obtained. It seems 

 to be well established that compounds presenting a close analogy to sugar 

 may be obtained by the metamorphosis of oleaginous, as well as of albuminous 

 substances within the body, of which we have examples in their continued for- 

 mation in the liver, when completely absent in the food, and even during the 

 last stages of inanition, and in their presence and gradual increase in the egg 

 during incubation. The small quantity of sugar naturally present in the 

 blood aids in retaining the carbonate and phosphate of lime in solution, and, 

 according to Hoppe, 2 assists that metamorphosis by which fat is generated 

 from the albuminous compounds. Most of the saccharine compounds are 

 soluble in water and alcohol, rotate the plane of polarized light to the right, 

 can be obtained in crystals, lose their water of crystallization at a tempera- 

 ture of 212, at a little higher temperature are converted into a blackish 

 substance termed caramel, and at a red heat are completely decomposed 

 into carbonic oxide, carbonic acid, carburetted hydrogen, acetic acid, 

 acetone, and other products. With oxide of lead and some other bases they 

 play the part of an acid ; on fermentation, they either yield alcohol and car- 

 bonic acid, or lactic, butyric, and formic acids. 



GRAPE SUGAR, C^H^O,, 4- H 2 O, crystallizes in warty masses which are 

 found under the microscope to consist of rhombic tablets. It is capable of 

 fermentation, and is especially characterized by its power of reducing all 

 easily reducible metallic oxides, as those of copper, bismuth, tungsten, and 

 molybdenum in alkaline solutions. It occurs naturally in the alimentary 

 canal as the product of the conversion of starch into sugar through the action 

 of the salivary, pancreatic, and intestinal juices, and from thence by absorp- 

 tion it gains entrance into the chyle and blood. It exists in small quantities 

 in the egg of the bird, in the arnniotic and allantoic fluids of the herbivora, 

 and occasionally in the urine of man. It is the chief or only saccharine con- 

 stituent of the urine in diabetes, and it may also be made to appear in the 

 urine by injury of the medulla oblongata. 



1 Ln9<>ns, 1859, vol. ii, p. 112. " Archiv f. Path Aunt, x, p. 140. 



