FIRST REPLY. 137 



formation of its bony structures. Albumen, fibrine and 

 caseine, are therefore rightly named by Liebig the exclusive 

 materials for nutrition ; they cannot be replaced by any 

 other substance ; when they are entirely withheld, the body 

 must necessarily die of starvation. But the components 

 devoid of nitrogen must also be present, as it were for fuel 

 on the hearth of organic life ; and these substances, which 

 are in common life also called food, Liebig appropriately 

 denominates materials for respiration. Comparing these 

 requisitions, which the animal body makes in behalf of its 

 maintenance, with the contents of plants which serve for 

 the food of man and animals, we find in all plants, in all 

 their organs, a certain amount of albumen dissolved in the 

 juices. In the inestimable gifts of Ceres, in the seeds of 

 the various kinds of grain, there always occurs more or less 

 of a substance which was formerly called gluten. Liebig* 

 and Mulder have pointed out that this resembles a mixture 

 of gelatine and animal fibrine. The earlier chemists disco- 

 vered in the Pulses a substance, which from the family in 

 which it was found, the Leguminosff, was called legumine. 

 We now know, from more recent researches, that this is in 

 no way different from animal caseine. Legumine and 

 gluten, or caseine and fibrine, possibly occur in small 

 quantity in the cells of all plants. 



The second class, the substances devoid of nitrogen, or ma- 

 terials for respiration, are no less widely distributed throughout 

 the vegetable world. When we review all the nutritive sub- 

 stances which mankind obtains from the vegetable kingdom, 

 we find three groups, the first of which is remarkable for the 

 great quantity of starch contained in the plants composing 

 it. To this group belong the Cereals and Pulses, the 



* See Liebig, " Chemistry and Physics in relation to Physiology 

 and Pathology," 8vo. London, 1847. 



