PROTEIN-BODIES. 209 



organic compounds which occur in such large quantities in its true 

 nutrient fluid, the blood. Herbivorous animals do not find any 

 substance analogous to gelatin in their vegetable food, and hence 

 they must generate it from the albuminous substances of plants. 

 All the solid bases of the animal organs consist of nitrogenous 

 matters, whigh can only originate from the albumen, on which 

 account we have named them derivatives of protein. Although 

 we may entertain no doubt that the albuminous substances are 

 gradually metamorphosed into the non-sulphurous constituents of 

 the gelatigenous tissues through the agency of the oxygen which 

 enters the blood, we are not able to advance anything beyond 

 mere conjecture in reference to the mode in which these processes 

 of metamorphosis are effected. We are still ignorant of the inter- 

 mediate stages through which the albumen or the casein un- 

 doubtedly passes before it appears in the form of a chondrigenous 

 substance, nor do we comprehend the internal connection, although 

 the metamorphosis of chondrigenous into the glutigenous tissue 

 takes place almost directly under our eyes. Although we may 

 succeed in exhibiting the result of these metamorphoses by very 

 simple formulae, we do not by that means the more clearly deter- 

 mine the actual nature of the process. 



The question whether the blood-fibrin constitutes the necessary 

 transition-stage from albumen to chondrin and gelatigenous tissue, 

 has been more than once propounded in the preceding pages (see 

 vol. i, p. 396, and vol. iii, p. 137), and we might with equal justice 

 inquire, whether the chondrin must everywhere precede the glutin 

 in the formation of connective tissue, the tendons, the skin, &c. ? 

 A very simple scheme of these forms of metamorphosis might 

 readily be deduced from a theoretical combination of the formulae 

 representing the composition of these substances ; but even if we 

 were accurately acquainted with the rational composition of all 

 these complex substances from a chemical point of view, our igno- 

 rance of the individual conditions of the process would prevent 

 our being able to decide with certainty which of the many possible 

 combinations and modes of representation expressible in formulae 

 should receive the preference. We have here to inquire if that 

 formula is the correct one, which imitates a process of decompo- 

 sition (or indicates the metamorphosis) in which atoms of oxygen 

 are added, and water and atoms of carbonic acid are abstracted ; 

 or whether the preference is due to that formula by which the 

 substance undergoing metamorphosis yields known excretory sub- 

 stances in addition to the main product ; or whether that is the 



VOL. III. P 



