1890-91. J AMPHIBIA BLOOD STUDIES. 2"2;3 



interaction, physical or chemical, of dye and object. It is of course not 

 even probable that the chromatin elements of all cells are chemically the 

 same except in the main outlines of their structural formulae, yet alum- 

 haematoxylin or alum-cochineal gives usually the same color reaction in 

 all. Here the effect is the same but the interaction may or may not be 

 the same in all cases. The subject belongs to borderland between 

 physics and chemistry and we can conceive that the interaction may lie 

 on one side or the other of any arbitrary line drawn to separate the two 

 domains without resulting in any visible difference in color. If different 

 colors should result when chromatin elements, for example, are stained 

 by a dye, then it may be safely inferred that the groups of atoms in the 

 variously stained elements are differently related to the groups of atoms 

 in the staining reagent. It might be suspected in such a case that the 

 difference in stain might depend on a difference in chemical composition 

 and this suspicion would become certainty, if a second dye were found 

 to act in a similar way towards the same chromatin elements. 



The difficulties which surround the solution of questions of this sort 

 are very numerous but they are multiplied when one multiplies the 

 methods of hardening or fixing tissues. These methods greatly vary 

 the effects of a single staining reagent on cellular structures. On this 

 account no conclusion of any great value has been drawn as to chemical 

 nature of any cellular substance from the employment of staining 

 reagents alone. On the other hand the employment in cytological 

 research of chemical reagents on objects under the microscope has not 

 been, even to a limited extent, successful. 



I have put forward all the difficulties which a research like this 

 presents and they have all through this work been before my mind. 

 I have resorted to the processes of staining, because the question 

 of the origin of haemoglobin is an all important one and because 

 I can see no other means of settling it. It may be said that the 

 means are insufficient. I can only say in answer that I have tried 

 to do the best with them and the conclusions given in this paper are 

 drawn from the results obtained by the employment not of a few but of 

 a very large number of methods of hardening and staining. It is only by 

 the employment of various staining reagents that one can avoid the 

 errors resulting from an adherence to one or to a few microscopical 

 methods and at the same time reach, usually, at least, measureably 

 certain conclusions. 



My first labors in this investigation were directed to finding a reagent 

 which would show the presence not only of haemoglobin, but of its 



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