GELATINOUS AND SACCHARINE PRINCIPLES. 173 



highly nutritious and is capable alone of the continued nutrition of 

 animals ; but an aversion to it is excited in animals obliged to subsist 

 entirely upon it. It is without odor or flavor, and is sometimes 

 nauseous; yet it has been given to animals, by Magendie, without dis- 

 taste, in doses of from 1850 to 2300 grs. daily, for 3 months, they pre- 

 serving excellent health. This appears to be opposed to the received 

 opinion, that one aliment alone is unfitted for prolonging life beyond 

 a short time ; but in gluten are found two or more different substan- 

 ces. It is to gluten that wheat flour owes its chief nutriment and 

 susceptibility of being made into bread. Gluten bread has of late 

 been made for diabetic patients ; and it seems well fitted for dispeptic 

 persons. 



The gelatinous principles of food have been thought a modification of 

 albumen, but these, with the tissues formed of them, are said to differ 

 in their properties and composition ; and the one has not been con- 

 verted into the other. The composition of proteine compounds is said 

 to be identical with the flesh and blood of animals, while those of 

 the gelatinous tissues are not; therefore the nutritive qualities of 

 the former are not the same. The albuminous tissues are insoluble 

 in water, and become hard by boiling, while those of gelatin become 

 soft and tremulous, forming gelatin or jelly. Such compounds as 

 soups, hashes and stews, from the gelatin they contain, are said to 

 be objectionable with dispeptic persons and invalids, in consequence 

 of the changes effected in the gelatin by heat ; but certain gelatinous 

 foods must be excepted. These gelatinous principles, however, are 

 more especially connected with animal food, of which it is not our pro- 

 vince now to speak. 



The variety of alimentary substances in the vegetable kingdom are 

 much greater than those of animals, and from the difficulty commonly 

 of determining the nutritive properties of these, our subject assumes 

 great importance with every reader. 



The saccharine alimentary principle. Of the general properties of 

 sugar, and as a product of the cane, we have spoken in the 2d part 

 of this volume, and also as an article of commerce and domestic use ; 

 it is, however, a constituent of vegetables, generally, and also of ani- 

 mals. The cereal grains contain portions of it, varying from 1 to 8 J 

 per cent. The fruits, and some of the roots especially, abound with 

 it. The highest proportion in fruits is the fig, 62.5, and of the roots in ,J """jft 

 the carrot juice evaporated to dryness, 93.71. Of that in the fruits we 

 shall speak under the head of fruits. It has heretofore been considered 

 a nutritious principle, but Liebig affirms that it is chiefly an element 

 of respiration. Brown sugar is said to be extensively adulterated with 

 sugar prepared from potato starch and from that of sago flour. 



The mucilaginous alimentary principle is extensively diffused in the 

 vegetable kingdom, in the form of gums. It exudes spontaneously 

 15* 



