310 The Philippine Journal of Science 1913 



slide and the cover-glass dropped upon it. Slight pressure may- 

 be exerted, if necessary, upon the cover-glass with the forceps 

 to cause the material to flow as a thin film between the cover- 

 glass and slide. If the stools be more or less formed, a small 

 drop of water should be placed upon the slide and a minute 

 portion of the stool rubbed up in it, forming a fairly thick sus- 

 pension of the faeces in the water, upon which the cover-glass 

 should be placed. A satisfactory preparation must be thin, but 

 there should not be an excess of fluid which will permit the 

 cover-glass to float about when the oil-immersion objective is 

 applied to it. A warm stage is not necessary for making the 

 examination. 



The advantage of a preliminary examination of the prepara- 

 tion with low magnification (Leitz 3 or Zeiss AA objective) 

 cannot be overestimated. It enables the examiner to make a 

 rapid survey of the whole preparation and to pick out the indi- 

 vidual entamoebse for examination with the oil-immersion ob- 

 jective. When the entamcebse are few in the preparation, they 

 can be found with difficulty, if at all, with higher magnification. 

 With a Leitz 3 or Zeiss A A objective and a 3 ocular, the enta- 

 moebse appear as round, oval, or irregular, colorless, and re- 

 fractive dots which with proper focusing stand out distinctly 

 in the background of the preparation. Practical experience will 

 enable the microscopist to distinguish them from certain other 

 bodies that are met with in stools. By applying the oil-immer- 

 sion objective — most conveniently used with the dry objective 

 on a revolving nose-piece — to every body in the preparation 

 which looks suspicious under low magnification, this experience 

 will soon be attained. Indeed, it is not only possible for the 

 experienced microscopist to identify an entamoeba with the low 

 magnification, but to distinguish a cyst of Entamoeba histolytica 

 from one of Entamoeba coli with a considerable degree of cer- 

 tainty by the difference in its size and refractiveness. 



A suspected entamoeba, having been located in the preparation 

 with the low-power objective, should then be examined with the 

 1/12 oil-imrnersion objective. With this magnification the enta- 

 moebse present certain morphological characters that enable the 

 experienced investigator to identify them whether they be in the 

 motile, resting, or encysted stage. 



The motile forms will give little difficulty, even to the novice, 

 since their movements are characteristic. 



The resting entamoeba is distinguished from other bodies 

 found in the stool by its size, distinctness, regularity of contour, 

 degree of refractiveness, and especially by its nuclear structure. 



