42 PARASITIC AMOEBA OF MAN. 



the examination of these organisms, a small drop of 

 the stool being placed in the centre of a cover glass 

 which is then inverted upon a hollow ground slide 

 and ringed with vaseline. If a film preparation is 

 used it should always be ringed with vaseline, for 

 unless this is done evaporation occurs and the prepa- 

 ration becomes useless. 



The preparation should be examined with a one- 

 sixth inch lens and a one- or two-inch eyepiece. For 

 the finer details regarding the structure of the cyto- 

 plasm and the nucleus, as well as the reproductive 

 changes, it is necessary to use the one-twelfth inch 

 oil immersion objective. 



Neutral Red. The use of a solution of 1/10,000 

 of neutral red is often of great service in those cases 

 in which the amoebae are few in number and for the 

 study of structural details. This solution is very 

 quickly absorbed by the amoeba?, coloring them pink 

 or red, and does not interfere with their movements 

 if it is not used in too strong a dilution. It is a 

 most useful method in distinguishing between para- 

 sitic amoeba? and leucocytes, as the latter do not stain 

 with this substance. In specimens in which the 

 amoebae are in scant numbers they are easily dis- 

 tinguished by the reddish color given them by the 

 neutral red, as other cells occurring in feces are not 

 colored distinctly by this dye. The dilution should 

 be made with normal salt solution. 



