36 SCIENCE PROGRESS. 



Hence it seems clear that the two methods ought both to 

 be employed ; for whilst the staining exhibits more or less 

 completely the structural arrangement of the substances 

 present, the microchemical method not only indicates some 

 at least of the important differences which exist between 

 the different structures revealed by the action of staining, 

 but it teaches us that certain of these same structures are by 

 no means so homogeneous in their nature as one might be 

 led to suppose relying on the evidence derived from stain- 

 ing alone. 



But those who pin their faith on stains sometimes seem 

 to forget that they are after all only employing a sort of 

 microchemical method themselves. For the fact that 

 different histological elements of the cell are distinguishable 

 by stais, implies the existence of a chemical dissimilarity 

 between them. And this becomes the more obvious when, 

 owing to periodically recurring changes in the cell, we 

 assert that this or that structure is growing or diminishing. 

 The investigator who is consciously proceeding on micro- 

 chemical lines is at least not so open to the charge of mere 

 empiricism as are those who look for salvation to 

 haematoxylin or the anilin dyes. He may be wrong in 

 supposing, for example, that the phosphorus within the 

 nucleus only occurs in the nuclein, just as he may be in 

 error in assuming that the substance nuclein itself really re- 

 presents a chemical substance in the same way that sugar 

 does. But he materially advances our knowledge of the 

 cell when he determines the fact that a body which fluctuates 

 in size as does the nucleolus, is composed of two substances 

 or groups of substances one of which is soluble in gastric 

 juice whilst the other is not ; and that further, the relative 

 size is, in the first instance, correlated with the amount of 

 substance which the fermentative action of pepsin can render 

 soluble. 



It is readily conceded that the bodies we call nuclein, 

 plastin, and the like, possibly may not, as stated already, 

 represent chemical molecules at all. This does not, how- 

 ever, diminish the interest attaching to the proof that this 

 or that substance is at one time present, while at another 



