222 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. II. 



A. METHODS OF STUDY. 



At the outset of an investigation like this, one has to answer the 

 question : How far can we rely on the different effects in staining 

 produced by a dye in determining the dissimilarity in composition of the 

 objects stained ? We can illustrate the question by a case in point : 

 safranin stains the nuclei of the red blood cells of Necturus orange-red 

 when they are fixed in a certain way, while the nuclei of ordinary cells 

 under the same conditions take a red color. Does this indicate that the 

 substance in the nuclei of the red corpuscles which is stained orange-red 

 is different in its chemical composition from that in ordinary nuclei i* 

 An affirmative and a negative answer are equally consistent with what 

 we know as yet of the relation between staining reagent and object stained. 

 It is quite possible to imagine the molecules of the staining reagent in 

 the object stained so placed relatively to the molecules of the latter that 

 though no chemical union results, certain kinds of the light rays become 

 absorbed in their passage through the object. It is further possible ta 

 conceive that variation of the distance of the molecules from each other 

 in the object stained may result in a variation of the rays transmitted. 

 Staining is in this sense a result of a physical condition, and as such 

 many consider it. It is easy also to understand that if the molecules of 

 one stained object should be different in structure from those of another, 

 the interarrangement of these with those of the same staining reagent 

 might affect the light transmitted in each of the two cases diffcrentU'. 

 In such the difference in color would depend on a difference in 

 chemical composition while the stain in itself would be referable to a 

 physical condition. In addition to these three possible modes in the 

 production of staining reactions there are two others, viz., the action of 

 the stained material in bringing about a change in the composition of 

 the staining reagent and the definite chemical combination of the staining 

 and stained material. The action of the stained object on the staining 

 reagent is illustrated by the effect produced by the chromatin of the 

 haematoblasts in the Amblystonia larvae on alum-haimatoxylin, the 

 usual color given by the latter reagent to ordinary nuclear constituents 

 being there turned to a slate tint. That chemical combination does 

 occur in the case of some reagents is shown by Uima's experiments with 

 several aniline dyes.* 



There being, thus, probably several ways by which a stain in an object 

 could be effected, it is manifestly impossible to prove in regard to any 

 particular dye, whether, when it stains a series of objects, the same 

 resulting colors in the latter are produced by the same or different 



*Arch. fiir Mikr. Anat., Bd. XXX. p. 38. 



