122 EXUDATIONS. 



jectures, notwithstanding some signal advances, that it scarcely 

 ever presents any starting point for chemical investigation. Few 

 attempts have been made to institute a micro-chemical analysis 

 even of the simplest pathological forms, and how can the chemist, 

 if he have no certain point to start from, arrive at correct conclu- 

 sions amidst opposing opinions, and the most variable forms and 

 the apparently similar products of the most widely differing pro- 

 cesses ? Let the chemist once obtain a fixed basis on which to 

 found his inquiries, and he will not fail to resolve purely physical 

 processes into tangible phenomena. 



It must be admitted, however, that the causes which prevent 

 the chemist from responding to the demands of the theoretical 

 physician do not depend solely upon deficiencies of physical proofs 

 and pathological observations, but upon an obscurity in the corre- 

 sponding departments of chemistry. We have endeavoured (see 

 vol. i, p. 19) to explain the causes which prevent chemistry from 

 participating in the investigation of pathological matters, and we 

 would indicate some points which may serve to justify the mode of 

 treatment we have adopted in this chapter, and to explain the 

 inefficiency of chemistry to solve pathological inquiries. 



We referred, in the introduction to histo -chemistry, to our very 

 deficient knowledge of the protein-bodies as the principal cause of 

 our inability to comprehend the elaboration of the tissues ; yet the 

 metamorphoses of the protein-bodies of the blood play the prin- 

 cipal part in the pathological exudations, cells, and tissues. It 

 therefore appertains to the chemist to follow the individual meta- 

 morphic stages in each of these bodies, as the histologist endea- 

 vours to trace the gradual formation of morphological elements 

 in their metamorphosis into cells and tissues. But whilst the parent 

 substances, and their relations to one another, are so imperfectly 

 known that we cannot, with any certainty, attempt to establish 

 for them a chemically rational formula, we have but little prospect 

 of being able to elucidate their proximate derivatives and the rela- 

 tions of affinity they bear to one another. The prospect would be 

 less discouraging if we were as well acquainted with the first stages 

 of metamorphosis as with the protein-bodies themselves. It should 

 be remembered how difficult it is to distinguish albumen and 

 casein when they are associated in the yolk of egg and elsewhere ; 

 that casein itself appears to be a mixture of several substances; 

 and lastly, that it is a matter of extreme difficulty, indeed almost 

 an impracticable operation, to extract chemically demonstrable 

 substances from pathological products whether recent or older 



