346 PROTEIN-COMPOUNDS. 



Origin. We have at present very little definite knowledge 

 regarding the origin of albumen from the nitrogenous food. No 

 doubt can be entertained that the chief source of the albumen of 

 of the blood is to be sought in the protein-compounds contained in the 

 food ; for independently of the circumstance that direct experiments 

 prove that animals cannot exist on food containing no protein- 

 compounds, we find from comparative statistics of the food which 

 has been taken, and of the nitrogenous matters expended in the 

 metamorphosis of tissue, (See " Nutrition " in the third volume,) 

 that the animal organism derives more than a sufficient supply of 

 protein-compound from the ordinary vegetable food. Although we 

 are not yet able to decide with absolute certainty on the incapability 

 of the animal organism to generate albumen from other sources than 

 protein-compounds, it yet appears highly probable that such is the 

 case. We are not even acquainted with the mode of origin of the 

 albumen of the blood from the allied protein-compounds contained 

 in the food, as casein, vitellin, fibrin, legumin, &c.: all we know is 

 that these bodies are converted by the process of digestion into 

 substances differing very much in their physical properties from the 

 above protein-compounds but resembling one another in their solu- 

 bility in water, their insolubility in alcohol, and their incapability of 

 coagulating. How and where these peptones become converted 

 into the normal albumen of the blood, are points on which we are 

 entirely ignorant, neither can we understand by what process 

 the albumen acquires its due quantity of sulphur, since these 



peptones, as I have convinced myself, for the most part contain 

 exactly as much sulphur as the substances from which they 

 originate. 



Uses. After what has been said of the occurrence of albumen, 

 it seems scarcely necessary to adduce any further proof of its 

 utility in forming and renovating the nitrogenous tissues of the 

 animal body. In fact the whole theory of nutrition rests on this 

 postulate. It is a question that has been much contested and 

 variously answered, whether albumen directly cooperates in the 

 formation of cells and the elements of tissues. Jul. Vogel* is an 

 especial supporter of the view that fibrinous exudations are alone 

 adapted for the formation of cells and tissues ; basing his opinion 

 on pathologico-anatomical experiments on exudations, and on the 

 fact that a small quantity of fibrin is contained in the lymph for the 



* Path. Anat. S. 80 ff. [or p. 107, &c., of the English Translation. Vogel's 

 opinion is'not quite fairly stated in the text. His remarks apply solely to morbid 

 developments. G. E. D.] 



