AMCEB.E OF THE INTESTINAL TRACT. 117 



be said that it generally measures from 25 to 50 

 microns in diameter. In the vast majority of in- 

 stances this parasite is considerably larger than Enta- 

 mceba coli, but, of course, the size varies with the 

 stage of development. However, I am of the opinion 

 that the size is generally under- rather than over- 

 stated by most writers. From my own observations 

 I believe that Entamceba histolytica, during its vege- 

 tative stage, is seldom less than 15 microns in 

 diameter, and generally much larger. If we remem- 

 ber that the average blood corpuscle measures 7 

 microns in diameter it will be at once apparent that 

 we seldom see amoebae in cases of dysentery which 

 are as small as one or two of these cells. It is also 

 well known that this species is phagocytic for red 

 blood corpuscles and it is not at all unusual to see 

 from 3 to 6 of these cells within the small amoebae. I 

 have observed amoeba? of this species containing from 

 10 to 30 red blood corpuscles and this gives a definite 

 idea of the large size of some of these parasites. A 

 measurement of 50 microns in diameter is not infre- 

 quently observed and the vast majority of these para- 

 sites measure from 30 to 35 microns, a much greater 

 average measurement than that of Entamoeba coll. 



These remarks do not apply to the encysted stage 

 of development or to the young spores. The cysts 

 measure from 10 to 20 microns in diameter, while the 

 spores average about 5 microns in diameter. 



