128 
Entamoeba histolytica 
to perform various experiments which would have been difficult had I not 
cultural strains in my possession. 
The “intra vitam” staining of the amoebae by a 1/10,000 solution of 
neutral red, described by Williamson and myself (1917), has proved a valuable 
aid in my researches. 
METHODS. 
The stained preparations were all made by the wet-film method. At 
different times I have tried most of the common fixatives, but obtained the 
best results with Schaudinn’s sublimate alcohol mixture or with Bouin’s 
fluid. For ordinary purposes the stains I employed were Heidenhain’s iron 
haematoxylin and Dobell’s modification described by him in 1914. This 
latter method is an extremely useful one, when rapid staining is desired, and 
the results are in every way equal to those obtained by the former. As 
counter stains to iron haematoxylin I have used alcoholic eosin, light green, 
and orange, G, all of which gave satisfactory results. I moreover employed at 
different times a number of other stains to those above mentioned, i.e. 
Ehrlich-Biondi, Delafield’s haematoxylin and eosin, acid carmine and nigrosine, 
Fleming’s tricolour, etc. 
The study of the nuclear changes, which occur during the life cycle of the 
amoebae, was beset with difficulties, among them being our lack of precise 
knowledge as to the reactions of substances such as plastin and chromatin. 
Methyl green acidulated with acetic acid was used with unfixed material, 
but Hertwig has cast doubt upon this stain being specifically chromatic; for 
he found that in Actinosjohaerium the nuclear material was not affected, but 
the plastin framework was coloured. 
I therefore tried the action of the various stains mentioned above. As a 
control in studying the staining effects I employed thin sections through the 
egg of the cockroach, which is known to possess a plastin nucleolus. 
The following table gives the reactions to the various stains. 
Stain 
Plastin 
Chromatin 
Delafield’s haematoxylin and eosin 
Red 
Blue 
Ehrlich-Biondi 
Maroon 
Green 
Acid carmine and nigrosine 
Blue 
Red 
Fleming’s tricolour 
Yellow 
Purple 
I have realised, however, that staining reactions alone must not be 
too much relied upon and that as Minchin says (1912) “A given body or 
grain in the cell cannot be definitely identified as chromatin, in all cases, by 
any chemical or physical test, but only by its relation to the life and develop¬ 
ment of- the organism as a whole, and more especially to the function of 
reproduction.” 
Keeping this standpoint in view I have not relied exclusively upon the 
staining effects of the various substances in the cytoplasm and nucleus of 
E. histolytica ; but have based my conclusions primarily on the behaviour of 
these substances during the life cycle of the organism: using their staining 
