No. I.] SYMPATHETIC GANGLIA OF VERTEBRATES. 29 



largely, however, because in my hands more definite results 

 were obtained with the methylene blue method. For the past 

 two years the latter method alone has been used, and the 

 results here presented are based exclusively on observations 

 made with it. 



Ehrlich's methylene blue method has so often been modified 

 in one way or another, that, in order to discuss it at all, it 

 seems quite imperative to take it up historically. Riese (i) 

 has, however, collected all the literature bearing on this method, 

 appearing before 1891 ; for the earlier modifications, therefore, 

 the reader is referred to this summary. Since that time the 

 most important modification of the method has been suggested 

 by Bethe (2), who, in recommending the use of ammonium molyb- 

 date to convert the unstable methylene blue compound, as formed 

 in fresh tissues, into one practically insoluble in water, alcohol, 

 and the imbedding media, has given us a method by which 

 methylene blue stained tissues may be imbedded in paraffin, sec- 

 tioned and counterstained at will. Too much cannot be said 

 for this important addition to the method suggested by Ehrlich. 

 The fixative suggested by Bethe has the following compo- 

 sition : 



Ammonium molybdate i grm. 



Aqua dest 10 c.cm. 



Hydrogen peroxide i c.cm. 



Hydrochloric acid i gtt. 



Into this solution, cooled to + 2° C, the stained tissues are 

 placed for four to five hours ; are then washed in water, dehy- 

 drated in alcohol, and imbedded in paraffin. Meyer (4) suggests 

 the omission of the hydrogen peroxide from the above formula, 

 because, as he believes, it has a bleaching action — " etwas 

 bleichend gewirkt hat." Bethe (3) in a more recent communi- 

 cation has, however, drawn attention to the fact that this strong 

 oxidizer is not, as such, present in the fixing fluid, because it at 

 once unites with the niolybddnsanren ammonmm, and this has 

 in the main lost the properties of the hydrogen peroxide. For 

 a further discussion of this question the reader is referred to 

 Bethe's (3) recent article. I may, however, add that before 

 Meyer's paper came into my hands similar conclusions had 



