SACCHARINE COMPOUNDS. 75 



ing-point, 97, and in separating from its alcoholic solution in nacreous glisten- 

 ing flocculi. 



44. It has been supposed that the substance of the Brain contains fatty acids 

 of a peculiar character, to which the terms Cerebric and Oleo-pJiosphoric have 

 been given by Fremy. Both of these have been said to contain a large quantity 

 of phosphorus, and the former to present the additional anomaly of a fatty acid 

 containing nitrogen. It appears probable, however, that in the analysis of Nerv- 

 ous tissue which gave the latter of these results, due care was not taken to 

 separate its fatty and its albuminous constituents ; and that the supposed Cere- 

 bric acid has no real existence, being merely an admixture of albumen with an 

 ordinary fatty acid. 1 Still, it appears that the fats of the brain contain phospho- 

 rus in some peculiar state of combination, and similar " phosphorized fats" are 

 found in the blood; and the belief formerly expressed by Berzelius, that the 

 phosphorized fats of the blood are chiefly contained within the red corpuscles, 

 has been recently confirmed by the analyses of Lehmann, who has found in the 

 red corpuscles of arterial blood 1.8 per cent., in those of venous blood no less 

 than 3.6 per cent, of fat extractible by ether, which, when incinerated, yielded 

 not less than 22 per cent, of ash, chiefly consisting of acid phosphate of lime. 

 In what state this phosphorus exists, however, is as yet uncertain. It will be 

 remembered that Prof. Liebig has lately ainrmed very decidedly, that phospho- 

 rus does not occur, either in the nervous tissue or in any organic compound, 

 except in the condition of phosphoric acid. It remains to be seen, therefore, 

 how far the fatty matters of the Nervous tissue are really peculiar to it, and 

 whether, if they are different from the ordinary fats, the latter may be meta- 

 morphosed into them. 



4. Saccharine Compounds. 



45. Of the organic components of the human body, it now only remains for 

 us to consider those of the Saccharine group, whose presence in the nutritious 

 fluids, so far as at present known, serves no higher purpose than that of supply- 

 ing material for the calorifying process, unless they can be indirectly made 

 available, by undergoing conversion into fat, as materials for the generation of 

 tissue. The form of Sugar which appears to be normally present (usually, at 

 least, if not constantly) in the Blood, is that known as Glucose, or "grape-sugar," 

 which is the saccharine compound that is most commonly present in fruits, and 

 that results from the transformation of starch by the action of acids, ferments, 

 &c. This substance differs from cane-sugar both in composition and properties j 

 for whilst the formula of crystallized cane-sugar is 12C, 11H, 110 (which is 

 considered as resulting from the combination of 120, 9H, 90, the equivalent 

 of anhydrous sugar, with 2HO), that of crystallized glucose is 12C, 14H, 14O, 

 this also containing 2 equivalents of HO in combination with the sugar itself. 

 Glucose is much less sweet than cane-sugar, is only half as soluble in water, 

 and is much less disposed either to crystallize, or to enter into combination with 

 oxide of lead and other substances. It has less, in fact, of those peculiar pro- 

 perties which so remarkably assimilate cane-sugar to inorganic compounds. We 

 accordingly find that the relations of the two sugars to the animal economy are 

 very different. Cane-sugar, when injected in any considerable amount into the 

 general current of the circulation, is neither assimilated nor removed by the 

 combustive process ; but, like soluble salts thus introduced, is speedily removed 

 by the kidney, being discovered in the urine. 3 On the other hand, a much larger 



1 Liebig's " Animal Chemistry," 3d edit., p. 257. 



2 This has been shown by various experimenters, among whom Dr. Percy ("Medical 

 Gazette," vol. xxxii.), Prof. Lehmann ("Physiological Chemistry," vol. i. p. 298), and 

 Dr. Cl. Bernard (" Compt. Rend." torn. xxii. pp. 534-537), may be particularly mentioned. 



