NUTRITION OP THE GRAMINIVORA. 



29 



sepaiated, and, except the elements of water, 

 no foreign element has been added to it in 

 this transformation. 



In many, especially in pulpy fruits, which 

 when unripe are sour and rough to the taste, 

 out when ripe are sweet, as, for example, 

 in apples and pears, the sugar is produced 

 from the starch which the unripe fruit con- 

 tains. 



If we rub unripe apples or pears on a 

 grater to a pulp, and wash this with cold 

 water on a fine sieve, the turpid liquid which 

 passes through deposits a very fine Hour of 

 starch, of which not even a trace can be 

 detected in the ripe fruit. Many varieties 

 become sweet while yet on the tree ; these 

 are the summer or early apples and pears. 

 Others, again, become sweet only after hav- 

 ing been kept for a certain period after gath- 

 ering. The after- ripening, as this change is 

 called, is a purely chemical process, entirely 

 independent of the vitality of the plant. 

 When vegetation ceases, the fruit is capable 

 of reproducing the species, that is, the kernel, 

 stone, or true seed is fully ripe, but the 

 fleshy covering from this period is subjected 

 to the action of the atmosphere. Like all 

 substances in a state of eremacausis, or 

 decay, it absorbs oxygen, and gives off a 

 certain quantity of carbonic acid gas. 



In the same way as the starch in putre- 

 fying paste, in which it is in contact with 

 decaying gluten, is converted into sugar, 

 the starch in the above-named fruits, in a 

 state of decay, or eremacausis, is trans- 

 formed into grape sugar. The more starch 

 the unripe fruit contains, the sweeter does 

 it become when ripe. 



A close connexion thus exists between 

 sugar and starch. By means of a variety 

 of chemical actions, which exert no other 

 influence on the elements of starch than 

 that of changing the direction of their mu- 

 tual attraction, we can convert starch into 

 sugar, but it is always grape sugar. 



Sugar of milk in many respects resembles 

 starch ; (13) it is, by itself, incapable of the 

 vinous fermentation, but it acquires the pro- 

 perty of resolving itself into alcohol and 

 carbonic acid when it is exposed to heat in 

 contact with a substance in the state of fer- 

 mentation (such as putrefying cheese in 

 milk.) In this case, it is first converted into 

 grape sugar ; and it undergoes the same 

 transformation, when it is kept in contact 

 with acids with sulphuric acid, for exam- 

 ple at the ordinary temperature. 



Gum has the same composition in 100 

 parts as cane sugar. (14.) It is distinguished 

 from the different varieties of sugar by its 

 not possessing the property of being resolved 

 into alcohol and carbonic acid by the pro- 

 cess of putrefaction. When placed in con- 

 tact with fermenting substances, it under- 

 goes no appreciable change, whence we 

 may conclude, with some degree of proba- 

 bility, that its elements, in the peculiar ar- 

 rang^ment according to which they are 

 united, are held together with a stronger 



force than the elements of Cut different kinds 

 of sugar. 



There is, however, a certain relation be- 

 tween gum and sugar of milk, since both 

 of them, when treated with nitric acid, yield 

 the same oxidized product, namely niucic 

 acid, which cannot, under the same circum- 

 stances, be formed from any >f :he other 

 kinds of sugar. 



In order to show more distinctly the simi- 

 larity of composition in these different sub- 

 stances, which perform so important a part in 

 the nutritive process of the graminivora, let 

 us represent one equivalent of carbon by C 

 (=75-8,) and one equivalent of water by 

 aqua (=112*4,) we shall then have for the 

 composition of these substances the follow- 

 ing expressions : 



Starch . . 

 Cane sugar 

 Gum . . 

 Sugar of milk 

 Grape sugar 



=12C4- 10 aqua. 

 =12 Of- 10 aqua-J-1 aqua, 

 =12 C4-10 aqua-j-1 aqua 

 =12 C+10 aqua+2 aqua. 

 =12 C-}-10 aqua-j-4 aqua, 



For the same number of equivalents of 

 carbon, starch contains 10 equivalents, cane 

 sugar and gum 1 1 equivalents, sugar of milk 

 12 equivalents, and grape-sugar 14 equiva- 

 lents of water, or the elements of water. 



XIV. In these different substances, some 

 one of which is never wanting in the fcod 

 of the graminivora, there is added to the 

 nitrogenized constituents of this food, to the 

 vegetable albumen, fibrine, and caseine, 

 from which their blood is formed, strictly 

 speaking, only a certain excess of carbon, 

 which the animal organism cannot possibly 

 employ to produce fibrine or albumen, be- 

 cause the nitrogenized constituents of the 

 food already contain the carbon necessary 

 for the production of blood, and because the 

 blood in the body of the carnivora is formed 

 without the aid of this excess of carbon. 



The function formed in the vital process 

 of the graminivora by these substances (su- 

 gar, gum, &,c.) is indicated in a very clear 

 and convincing manner, when we take into 

 consideration the very small relative amount 

 of the carbom which these animals consume 

 in the nitrogenized constituents of their food, 

 which bears no proportion whatever to the 

 oxygen absorbed through the skin and lungs. 



A horse, for example, can be kept in a 

 perfectly good condition, if he obtains as 

 food 15'lbs. of hay and 4 Ibs. of oats daily. 

 If we now calculate the whole amount of 

 nitrogen in these matters, as ascertained by 

 analysis (1-5 per cent, in the hay, 2*2 per 

 cent, in the oats,) (15) in the form of blood, 

 that is, as fibrine and albumen, with the due 

 proportion of water in blood, (80 per cent.,) 

 the horse receives daily no more than 4 oz. 

 of nitrogen, corresponding to about 8 Ibs. of 

 blood. But along with this nitrogen, that 

 is, combined with it in the form of fibrine or 

 albumen, the animal receives only about 14 

 oz. of carbon. Only about 8 oz. of this can 

 be employed to support respiration, for with 

 the nitrogen expelled in the urine there are 

 C* 



