100 AZOTISED SUBSTANCES. LECT. V. 



the latter. They appear to differ from each other, merely 

 in the small quantity of phosphorus and sulphur which they 

 contain. If these two bodies be abstracted, there remains 

 a principle common to the three, and which has been termed 

 by Mulder, proteine ; the formula of which, as adopted by 

 Liebig, is 



<^8 H 36 N 6 O 14 . 



/ 



We must, then, regard these substances, although en- 

 dowed with very different physical properties, as isomeric, 

 and as modifications of proteine.* 



The other important fact discovered by Dumas and Liebig 

 is, that vegetable albumen is identical with animal albumen; 

 that, in the farina of the cereal grains there exists a substance 

 analogous to caseine ; and, that in gluten there is a substance 

 like animal fibrine. 



There is not, then, any essential difference between the 

 aliments of the herbivorous, and those of the carnivorous 

 animals, except that the first is drawn from plants, the 

 second from animals. 



Since the composition of the blood, as well as the greater 



* Since the delivery of Matteucci's lectures Liebig's views respecting 

 Mulder's theory of proteine have undergone an entire change, and he now 

 declares this theory to be untenable and fallacious. In his Researches on 

 the Chemistry of Food (1847) he observes, that "it now appears, as the re- 

 suit of the more accurate investigations of Laskowski, Ruling 1 , Verdeil' 

 Walther, and Fleilmann, that the amount of sulphur present in the blood 

 constituents is three times, in many cases, four times, as great as the ap- 

 parently well-established analysis of the author of the proteine theory had 

 indicated. It further appears, that a body, destitute of sulphur and having 

 the composition of proteine, is not obtained by the methods given by 

 Mulder ; that fibrine differs in composition from albumen ; that the albumen 

 of ejrgs contains not less, but more sulphur than the albumen of the blood." 

 (p. 27.) He also asserts that, " the existence of phosphorus, as an essential 

 element of [some of] these substances [fibrine and albumen,] has not been 

 in any way established." (p. 23.) J. P. 



