i84 RESEARCH IN PROTOZOOLOGY 



serum of individuals infected with this parasite, thus proving 

 that antibodies are produced to this infection, and explaining the 

 occurrence of many cases of infection with this parasite in which 

 symptoms are absent or so mild as not to attract attention. This 

 apparently specific reaction has been found useful in the diagnosis 

 of infections with E. histolytica and it is probable that further 

 work in perfecting the extracts used as antigens may render the 

 complement fixation test for E. Jiistolytica of general clinical 

 value as a routine diagnostic test. 



Historical. Before considering the subject of complement fixa- 

 tion a brief review of what has been accomplished in the serology 

 of infections with Endauiaba histolytica may be of interest. 



Perhaps the first contribution of moment upon the serology of 

 these infections was that of Izar (1914), who claimed to have 

 obtained complement fixation reactions with the blood serum of 

 five human infections with E. Jiistolytica and the blood serum of 

 three cats infected with this parasite, using as an antigen aqueous 

 extracts of the feces of infected cats and the pus from a liver 

 abscess in man. His work was repeated in. 1920, by Hage, who 

 was unable to confirm Izar's results, but the lack of confirmation 

 may have been due to numerous factors, as variations in the 

 technique, the amount of antigenic substance in the antigens 

 employed by the two workers, and the character of the infection 

 in the individuals tested. In the light of the work recorded in 

 this contribution it is extremely doubtful if the antigens em- 

 ployed by Izar would prove of clinical value in the diagnosis of 

 amoebic infections, but it is reasonable to believe that he did 

 obtain complement fixation with the antigens that he used in his 

 work. 



More recently, Wagener (1924) has recorded her results in 

 an attempt to devise a precipitin test for E. Jiistolytica in experi- 

 mentally infected kittens, using as an antigen scrapings of amoebic 

 ulcers of the colon of the cat. This work was adequately controlled 

 and resulted in the demonstration that in the blood serum of cats 

 infected for a week, or longer, after the amoebae were observed 

 in the stools, there occurred antibodies which gave a positive 

 precipitin reaction with such antigens and that the blood of normal 

 cats, or cats infected for less than a week after the appearance of 

 the amoebai in the stools gave negative precipitin reactions. 



The preparation of the antigen, the controls employed, and 



