1^90-^tl.] AMPHIBIA BLOOD STUDIES. 231 



red discs, and especially when employed on the spleen, is Erlicki's Fluid. 

 This, combined with the Indigo-carmine Fluid described in the foregoing 

 pages, gives a remarkably sure means by which one can determine the 

 presence of the pigment. The red cells of the spleen present with this 

 fixative reagent and the staining fluid a uniformly grass-green disc 

 in which no structural elements can be observed and a nucleus which 

 may be either carmine red or grass-green, or of a shade in green. 

 Sometimes the nucleus presents a network as deeply grass-green as the 

 substance of the disc, while the substance in the meshes of the net-work 

 is red. These different effects obtained on the nuclear structures are 

 not due to artificial or physical conditions such as the early or late 

 action of the fixative reagent, for all the described features can be found 

 in the nuclei of cells placed side by side. Without raising the question 

 at present whether there is any haemoglobin in the nucleus, a question 

 which might be prompted by an observation already made above, it may 

 be concluded that the nuclei of the red cells are not all similar in their 

 chemical relations towards sulphindigotate of sodium. This conclusion 

 may be also drawn from a study of cover-glass preparations of blood in 

 which it is often easy to see a grass-green network in the carmine-red 

 nuclei of the red cells. 



In cover-glass preparations fixed with osmic acid vapor in which the 

 layer of blood is very thin, the haemoglobin is also well preserved. 

 Here the nuclei of the red cells have, after the employment of Indigo- 

 carmine Fluid, a grass-green network in the meshes of which the 

 substance is faint red. In similar cover-glass preparations in which the 

 layer of blood is comparatively thick the discs of the red cells are 

 grass-green, the nuclei distinctly red with a green net-work. In cover 

 preparations on which the solution (i%), instead of the vapor of osmic 

 acid, was used the same staining reagent gave red nuclei and grass-green 

 discs to the red cells. 



In cover preparations of the blood made with corrosive sublimate 

 solutions the Indigo-carmine Fluid stained the discs and nuclear network 

 deep blue green, while the substance in the meshes of the net-work is 

 colored from a light to a deep red, oftener the former. Frequently, 

 wnth an ordinary power such as a D of Zeiss, very many, or nearly all 

 nuclei of the red cells appear homogeneously red, but with the employ- 

 ment of an oil immersion (yV in.) the presence of the blue green network 

 can be distinctly determined. 



Flemming's Fluid, Miiller's Fluid and chromic acid dissolve the haemo- 

 globin out of the red discs in cover-glass preparations of the blood and 



