200 THE PARASITISM OF 



immersion in Miiller's fluid or chromic acid, and spirit. Being 

 now accustomed to recognise this parasite, faint traces of them 

 were observed in places, but nothing satisfactory nor convincing. 

 The reason is, I beheve, that the material was not properly pre- 

 pared for the purpose. 



Methods of Fixing. — The way in which I now attempt to 

 proceed is to obtain the material as soon as possible from the 

 operating table, fresh specimens being much more satisfactory to 

 handle afterwards than material obtained from the post-mortem 

 room. Pieces of small size {\ inch square) are then placed, one 

 set in Flemming's fixing solution, and another set in corrosive 

 sublimate, or in Foa's fixing solution. After remaining in the fixing 

 solution for a sufficient time, the pieces of tissue are thoroughly 

 washed, hardened in successive strengths of alcohol, embedded in 

 paraffin, and cut in the usual manner. 



Methods of Staining. — The staining reagents which have been 

 found most useful are hsematoxylin (Ehrlich) alone, or with some 

 ground stain (rose bengale, eosin, etc.), and the Biondi triple stain. 

 The reason for having the preparations fixed in two different ways 

 is that Flemming's solution fixes the cell elements more sharply 

 and definitely than any other not containing osmic acid, and if the 

 parasites are present in the piece of tissue to be examined one 

 feels sure of finding them. The staining reaction, however, with 

 an osmic acid fixing reagent is not very brilliant, and for this 

 reason it is well to have the other series of preparations at hand 

 to obtain staining reactions if required. 



Flemming's solution, followed by haematoxylin, gives, to my 

 eyes, as good results in the way of sharpness of definition as can 

 be obtained ; the epithelial cell nuclei take up the haematoxylin in 

 the normal way, but do not bear the same tone of blue as that 

 shown by the parasites ; in the case of the " Biondi " reagent — so 

 strongly recommended by Dr. Ruffer and Mr. Walker — the dis- 

 tinctive colouring is much more striking and beautiful, and its 

 results are well seen in the beautiful drawings accompanying their 

 paper. 



I would add, in reference to the matter of staining, that the 

 secret of discovering the bodies is in the fixing and hardening of 

 the preparations ; no precaution should be thrown aside in carry- 



