Natrilive Matter of Grasses. 



173 



The class of non-nitroirenous principles, omittin<r those which 

 possess no general importance to our present purpose, includes 

 woody fibre, starch. g"um, sua-ar, mucilage, pectic acid, 6:c., toge- 

 ther with different oily or fatty matters. Many of these are 

 soluble in water, as suirar. gum. <S:c., whilst woody fibre, pectic 

 acid, and starch, are insoluble in cold, and the two former even 

 in hot water. 



It is now almost universally conceded that the nitrogenous 

 principles in plants are assimilated, or adopted as it were ijv the 

 animal economy with little alteration, being, bv processes that are 

 easiU' conceived, converted first into blood, and then into liesh 

 and muscle, all of which they so closely resemble in composition 

 and properties. Little is known as to the relative adaptation of 

 these ditferent substances for assimilation into the animal bodv — 

 whether vegetable albumen or vegetable casein, for instance, is 

 more susceptible of conversion into flesh : and for the present, 

 at least, we must be content to regard them m a general wav as 

 equally valuable in this respect. But this much is known, that 

 the presence of members of the nitrogenous class is essential to 

 the composition of nutritive food, and tiiat starch or sugar alone 

 is quite unfitted to support, much less to increase, the animal 

 frame. On the other hand, the class of non-nitrocrenous sub- 

 stances is equally necessary for the support of respiration and 

 animal heat, and the production of fat. But, whilst physiologists 

 make no great distinction between the members of the llesh- 

 forming class, they allot to one set of non-nitrogenous principles 

 the oihce of supplying the elements of respiration, and to another 

 that of producing fat. ]Vluch dispute has existed upon this point 

 — some physiologists asserting that the sugar and even the starch 

 of their food mia'ht serve to form fat in animals, whilst others 

 have held the belief that the fat which was deposited in the body 

 must have pre-existed as such in the food. The question seems, 

 however, to have resolved itself into this — that starch, gum, 

 sugar, and oily and fatty matters, may each and all contribute to 

 the respiratory and heat-producins: functions : whilst, in the form- 

 ation of fat. the ready-formed fattv matters take precedence : 

 and. ]n their absence, first suiiar and then starch mav be emploved 

 for that purpose. 



From what has been now said, it will appear that the plan 

 adopted by Z^Ir. Sinclair for the determination of the nutritive 

 properties of the grasses Avas defective in more wavs tiiaii one. 

 In the first place, it afforded no kind of information as to the 

 relative quantity of flesh-forming, fattening, and heat-producing 

 compounds existing in the plants : and, in the second, it did not 

 even give a correct idea of the proportion of all these substances 



