STUDIES WITH ENDAMCEBA HISTOLYTICA 187 



ice-box over night, as most strongly positive cases are still positive 

 at the end of this time. 



As controls alcoholic extracts of all the bacteria growing in 

 the cultures with E. histolytica, both aerobic and anaerobic, have 

 been prepared and used in the same manner as the antigenic ex- 

 tracts and have always given negative results in the test. Their 

 use has now been abandoned because of the uniformly negative re- 

 sults obtained in a very large series of experiments and our ex- 

 perience has proven that, while desirable, these bacterial extracts 

 are not necessary as controls in the practical application of the 

 test. 



In the experimental work the sera tested were taken at random 

 from specimens submitted to the serological laboratory of the 

 Army Medical School for the complement fixation test for syphihs 

 and such sera are used continually as controls of the sera sub- 

 mitted by clinicians for the complement fixation test for E. Jiis- 

 tolytica. 



After testing the blood sera, a specimen of feces is always 

 requested from each patient tested, whether the result is positive or 

 negative, and this is examined microscopically, culturally, and, if 

 necessary, by the sedimentation test for the cysts of E. Jiistolytica. 

 Thus all of the results reported in this contribution have been 

 checked by such examinations of the feces of the individual sup- 

 plying the blood serum tested. 



Results of the Couiplcuieiit Fixation Test. At the time of writing 

 570 blood sera, from as many individuals, have been tested, and 

 the results checked by an examination of the feces. Of these sera, 

 sixty-one or 10.7%, gave a positive reaction, and 509, or 89.2%, 

 gave a negative reaction. Of the positive cases, fifty-three gave a 

 four-plus reaction, and eight gave a three- or two-plus reaction. 

 The large percentage of positive cases giving absolute inhibition 

 of hemolysis, or a four-plus reaction, is noticeable with this test 

 and renders it very easy to read and evaluate. 



Of the sixty-one positive cases, a check of the feces for End- 

 amocha histolytica resulted in the demonstration of this parasite 

 in fifty-five individuals, or 90.1%. In six individuals we were un- 

 able to demonstrate this organism in the feces although in two of 

 these there was a history of amoebic dysentery. 



Of the sixty-one positive cases, eight were mixed infections 

 with Endania:ba histolytica and Endaniwha coli; two mixed infec- 



