220 METAMORPHOSIS OF TISSUE. 



they are employed in maintaining animal heat, or are entirely 

 removed from the body with the urine and sweat, whilst on the 

 other hand equally efficient means serve to render the passage of 

 deleterious matters from the blood into the parenchyma of the 

 organs extremely difficult, and to facilitate in an equal degree 

 their expulsion from the organism by the aid of the urine and 

 sweat. 



Moreover, the carbo-hydrates, or rather the sugar, may very 

 probably accomplish some other less striking functions before their 

 conversion into acids ; thus for instance, the sugar in the alkaline 

 fluid of the blood certainly contributes its share to the solution of 

 the carbonate and phosphate of lime, as is very obviously mani- 

 fested in the development of the embryo in the egg of the bird. 

 It long remained a mystery to the older observers, how the salts of 

 lime could be augmented in the embryo, and it was believed or 

 assumed that the lime must be derived solely from the shell of the 

 egg; but even if some acid salt of lime may be formed during the 

 period of incubation, and may pass into the juices of the developed 

 germ, yet the sugar, when present, combines with the alkali or lime 

 in the alkaline fluid, and may then dissolve the carbonate of lime 

 as a compound of sugar with lime or soda, a fact which has been 

 long known and has been recently brought to notice by Barreswil.* 

 May not the capacious size of the liver of the chick during the 

 latter days of incubation be the cause of the greater amount of 

 sugar which is found in the albumen of the egg at that period than 

 before incubation ? And may we not conjecture that the liver of 

 the fetus of the mammalia, which, notwithstanding its size, 

 secretes very little bile, may serve to generate sugar from the pro- 

 tein-bodies ? This sugar, which I have determined with the 

 greatest exactness in the foetal blood of calves, is assuredly not 

 formed in the liver simply to be consumed, for even if the albumi- 

 nous substances in the foetus are partially appropriated to the 

 maintenance of internal heat, they would hardly be first decom- 

 posed into sugar and other substances in order to. effect this pur- 

 pose. The foetus, which requires sugar quite as much as the young 

 animal during lactation, generates it in the organs designed for 

 that purpose, and the blood of the foetus with its small amount of 

 alkali has less tendency to decompose sugar than the more alkaline 

 blood of breathing animals (see vol. ii. p. 255). 



We have already frequently referred to the application of sugar 

 to the formation of tat, and we will, therefore, simply observe that 

 * Mouiteur Industrie!. 1850, No. 1542. 



