OF THE ALIMENTARY TRACT 39 



and makes them more conspicuous. It also allows 

 the nuclei to become visible as colorless rings against 

 the yellow-brown background. 



When a suspicious body is located with the low- 

 power lens, the higher dry magnification will usually 

 reveal its structure. 



If the cysts found show four round nuclei with tiny 

 central karyosome it is Endamoeha histolytica. The 

 main confusion is with the cyst of Endamoeha coli; 

 it has eight nuclei. This simple mathematical propo- 

 sition, so difficult to get across to medical labora- 

 torians, is the most important thing in the diagnosis 

 of amoebiasis, it is the sole conclusive point in the 

 chronic case, practically considered. 



Of course, there may be a mixed infection and one 

 should not cease search for this cyst until satisfied of 

 its absence, regardless of what else may be found. 



In addition to Endamoeha coli much confusion 

 arises from that ubiquitous stool inhabitant, Blasto- 

 cystis. A little experience, however, will lead one to 

 pass this by as he would foreign particles. Because 

 of this common confusion consideration of Blasto- 

 cystis in an appropriate place is given in this book, 

 although it is not a protozoon. Suffice it to say here 

 that it is commonly very numerous in a liquid stool, 

 is very common in any, is of widely variable size, 

 rounded, ovoid, or elongate. It usually has a trans- 

 parent rim sharply defined from the main body, 

 which is hyaline, stains brown with the iodine and 

 contains no nuclei like those of the amoebae. Study 



