INTRODUCTORY REMARKS. 123 



exudations. Even in those cases in which the chemist succeeds 

 in extracting one or other of these substances, he seldom obtains 

 satisfactory evidence of their chemical purity, without which they 

 are wholly inapplicable for a true chemical investigation. A chemist 

 cannot be satisfied that he knows a substance until he has sub- 

 mitted it to an elementary analysis, and can attain, at all events, an 

 approximate determination of its atomic weight ; in fact, a body 

 which has been submitted by the chemist to a few reactions only, 

 however striking they may be, but for which he is unable to 

 establish a formula based upon elementary analysis, may be almost 

 considered as unknown to him. In this sense (and in exact 

 investigations we can only take this view) all substances which 

 manifest themselves as transition-stages from the protein- bodies of 

 a plastic exudation are wholly unknown to us, and must remain 

 equally unexplained until we are able to elucidate the mystery of 

 protein. 



Although there may be an established conviction that the 

 chemist is still unable to trace the metamorphoses of plastic matter 

 in the exudations, and to note the processes by means of which one 

 or other form is produced, we may be disposed to inquire what 

 qualitative alterations, what heterogeneous constituents, and what 

 special substances are to be perceived in the inflammatory, or 

 the so-called specific exudations. 



Like others, we have undertaken numerous investigations of 

 this subject in obedience to the requirements of physicians, and 

 we have succeeded in proving the presence of true biliary sub- 

 stances both in plastic and non-plastic exudations under many 

 different relations, which scarcely admit at all times of being fully 

 demonstrated, and have exhibited taurocholate of soda as well as 

 beautiful crystals of glycocholate of soda. Urea, sugar, certain 

 extractive matters, &c., may be shown to exist in nearly all exuda- 

 tions. However interesting such observations may be in many 

 respects, the presence of these substances can scarcely, as far as 

 we are at present able to judge, have any important influence on 

 the metamorphosis of the fluid exudation, or any special significa- 

 tion in respect to the formation of this or that form of tissue. 

 What additional point have we ascertained if even we succeed in 

 showing that cystine forms the principal constituent in tuberculous 

 masses, succinic acid possibly in cancerous growths, or some other 

 unusual substance in other diseased matters, if no connection can 

 be traced between the presence of such a substance and the other 

 circumstances of the case ? The qualitative examination of patho- 



