TEROXIDE OF PROTEIN. 391 



Physiological Relations. 



According to Mulder this body exists in normal blood and in 

 all fluid exudations, and hence also in pus ; and its quantity is very 

 considerably increased in the blood in inflammatory diseases. He 

 regards the pyin discovered by Guterbock in pus as altogether iden- 

 tical with this substance ; but if for the reasons we have already 

 given in reference to testing for teroxide of protein, we cannot re- 

 gard it as positively decided that this substance occurs in all these 

 animal fluids, yet it is probable from the mode in which it is arti- 

 ficially prepared, that a substance which is formed from albumen or 

 fibrin in warm water exposed to the air, also occurs in the blood 

 where the above named substances which yield it, are exposed to 

 similar influences. If more accurate investigations confirm the 

 existence of this teroxide of protein in the manner that Mulder 

 supposes, we shall then acquire a knowledge of an important inter- 

 mediate link in the metamorphoses of the animal tissues, and in 

 particular we shall have considerably approximated to the yet un- 

 solved problem of the conversion of albuminous bodies into bodies 

 yielding gelatin, or of fibrin into tissue. 



DERIVATIVES OF THE PROTEIN-COMPOUNDS. 



The bodies of this group present very great differences in their 

 physical and chemical properties ; except that they all contain 

 nitrogen, and that they occur only in the animal body, where they 

 form the chief groundwork of the tissues, there is scarcely a point 

 of general resemblance between them ; in their behaviour towards 

 acetic acid and ferrocyanide of potassium, and towards concentrated 

 hydrochloric and nitric acids they exhibit none of the essential 

 characters of the protein-compounds. Only four of these sub- 

 stances have as yet been accurately studied, although regarding even 

 their intimate chemical constitution there is as much doubt as in 

 the case of the protein-compounds. 



