24 



while another 100 having a covered shed and a yard to run 

 into at pleasure, only eat each 20 lbs. of Swedes, and gained 

 2 lbs. each more of flesh than the former.* 



But, besides the waste of food induced by the want of shel- 

 ter, must be added the want of economy in not using, to- 

 gether with turnips, food which contains more nitrogen. 

 " The increase of the mass of the body (says Liebig), the 



development of its organs, and the supply of waste, all 

 " this is dependant on the blood, i, e., on the ingredients of 



the blood, and those substances only can properly be called 

 " nutritious, or considered food, which are capable of conver- 

 " sion into blood. To determine, therefore, (he says) what 

 " substances are capable of affording nourishment, it is only 

 " necessary to ascertain the composition of the food, and to 



compare it with the ingredients of the blood. But the 

 " chief ingredients of the blood contain nearly 17 per cent. 

 " of nitrogen, and no part of any organ of the body contains 

 " less than 17 per cent, of nitrogen; and animals cannot be 

 " fed on matters destitute of nitrogenised constituents. But 



vegetable fibrine, vegetable albumen and caseine, are the 

 " true nitrogenised constituents of the food of graminivorous 

 " animals/' And the learned Professor's book contains the 

 discovery that these three vegetable substances contain the 

 same organic elements united in the same proportion by 

 weight, and, what is still more remarkable, are identical in 

 composition with the chief constituents of the blood, viz., 

 animal fibrine and albumen. These vegetable principles con- 

 tain the chief constituents of blood, fibrine and albumen 

 ready formed. Vegetable fibrine and animal fibrine, veget- 

 able albumen and animal albumen, hardly differ, even in 

 form. " If these principles be wanting in the food, the 



* Experiments regarding the relative feeding properties of different kinds of 

 food, are of no value unless the temperature of the places in which the animals 

 are fed, be the same. 



