76 CHEMICAL COMPONENTS OF THE HUMAN BODY. 



quantity of grape-sugar may be injected into the general circulation, without any 

 trace of it becoming detectable in the urine ;* hence, it is obvious that this is 

 applicable to some purpose within the system, and does not require to be cast 

 out as a foreign substance. The presence of Glucose in the Chyle and Blood 

 appears to depend upon the presence of either starch or sugar in the food. The 

 transformation of starch into glucose is effected, as will hereafter be seen, during 

 the passage of the alimentary matter along nearly the whole length of the canal ; 

 this conversion being begun by the saliva, and continued by the pancreatic and 

 other secretions which are poured into the intestinal tube. That the glucose 

 thus formed is partly taken up by the lacteals, appears from the experiments of 

 Trommer and Lehmann; 3 but that it is also more directly absorbed into the 

 blood-vessels, like other soluble matters, by simple endosmose, has been deter- 

 mined by M. Cl. Bernard, 3 who has always met with distinct traces of cane-sugar 

 in the blood of the vena portse of animals that have been fed upon it ; and there 

 appears to be a special provision in the liver for the conversion of the sugar thus 

 absorbed, into the form in which its presence in the blood can be best tolerated 

 until it is eliminated by the respiratory process. For it appears from the expe- 

 riments of M. Bernard (loc. cit.) that, although cane-sugar is rapidly eliminated 

 by the kidneys when it is injected into the general circulation, it may be injected 

 in considerable amount into the portal system, without producing any such ef- 

 fect. When large quantities of saccharine or of amylaceous matters have been 

 employed as food, the general mass of the blood is found to contain an apprecia- 

 ble portion of sugar, as has been shown some time since by Prof. R. Thompson, 4 

 and M. Magendie. 5 But it has been recently shown by M. Bernard, that a sugar 

 nearly allied to glucose is a constant constituent of the blood drawn from the 

 hepatic vein, ascending cava, right auricle, and pulmonary artery of all animals, 

 whether they have been fed upon amylaceous or saccharine substances, or upon 

 food entirely destitute of these principles ; a fact of the highest interest, of 

 which the explanation will presently appear. 



46. From the readiness with which Glucose undergoes transformation into 

 lactic acid, in the presence of azotized compounds, there can be little doubt that 

 this change is continually taking place in the living body ; and it is probably in 

 the form of lactic acid, that glucose is rendered subservient to the maintenance 

 of animal heat by the combustive process. Such, therefore, we may consider to 

 be the usual destination of the Saccharine compounds introduced as food. But, 

 as already mentioned, there is ample evidence that, when there is a deficiency 

 of fatty matters in the food, these may be formed by a metamorphosis of its sac- 

 charine constituents ; and with this change, there is a strong probability that 

 the Liver is chiefly concerned. But further, evidence has been recently obtained, 

 that this important organ can actually generate Sugar from other than amyla- 

 ceous compounds ; for it has been ascertained by M. Bernard, that the substance 



1 The following are given by Magendie as the proportions in which different sugars 

 require to be injected into the jugular, in order that they should be discoverable in the 

 urine. 



Cane-sugar ;> -a** ;;y -. . . *,.' v :; ' ; 1 

 Mannite . ^{ , ,v*. .. Jj .- .., j ..', . * ,:; '*-.!, ;. ' ; .'.. 1 



Sugar of Milk . ' v , c . " . '' ,. \ ... . , . f , ; . 5 



Glucose . ,.* . : ,*.. fr .', .*, : .' V '..' . 50 

 Sugar of the Liver . .. . v J '. . ,'!-'' . 240 



Thus we see that 50 times as much of glucose as of cane-sugar, and nearly 5 times as 

 much of liver-sugar as of glucose, is required to produce this effect. (See " L' Union 

 Medicale," 1849, Nos. 72, 75, 79.) 



2 "Physiological Chemistry," vol. i. p. 289. 



* "Gazette Medicale," 1850, No. 5. 



4 "Philos. Magaz.," April and May, 1845, and "Medical Gazette," Oct. 10, 1845. 



* "Compt. Rend." torn. xxx. pp. 191, 192. 



