OF THE ALHIENTARY TRACT 37 



to the species by any except the most experienced 

 and at times by them, while this painstaking method 

 of staining is usually not attended by striking success 

 except by one constantly practiced in it. 



It is considered a good practice in medical diagnosis 

 to have some routine procedure like the following: 



Unless there is diarrhoea, administer a saline 

 cathartic to produce a liquid stool. Oil renders a 

 specimen unfit for examination, both fresh and 

 stained. Examine immediately, i.e. while fresh and 

 without allowing the stool to cool, portions from dif- 

 ferent parts of the stool, as described above. Use a 

 mechanical stage so as to be certain of covering the 

 whole preparation. There has been much said about 

 the frequency with which amoebae are not to be 

 found in the stool of an infected person and it is well 

 know^n that the fifth or sixth examination of a stool 

 may show an amoeba for the first time. How^ever, 

 a fresh liquid stool, produced and examined under the 

 above conditions, will seldom fail to reveal any ex- 

 isting infection. If two or three repetitions of the 

 procedure fail to show any protozoon it may be or- 

 dinarily accepted that there is no infection. 



So much emphasis has been placed upon the neces- 

 sity for a number of stool examinations before a 

 negative may be declared that it is often considered 

 by practicing physicians that stool examination for 

 protozoa is an impractical procedure. 



For routine practice one or two repetitions of a 

 negative finding, after two or three days, under strict 



