688 INFECTION AND IMMUNITY. 



grow with a variety of bacteria. Growth occurs 

 only on the surface of the agar plates. When a 

 pure strain of ameba is grown with a single species 

 of bacterium the culture is spoken of as a "pure 

 mixed culture." 



Amebic dysentery is primarily a disease of the 

 tropics, where the natural conditions are favorable 

 for the growth of the amebae and their conveyance 

 to man. 



First found by Lambl (1860), then by Cunning- 

 ham and Lewis (1870), the organisms were de- 

 scribed more accurately and given the name of 

 Amoeba coli by Ldsch (1875). Losch recognized 

 them as the cause of a chronic form of dysentery, 

 but it was Kartulis, in particular, who found the 

 amebas constantly in the discharges and ulcers of 

 the disease, and also in the liver abscesses which 

 accompany the infection. Since amebae demand 

 the presence of living bacteria for their growth, 

 their independent pathogenic nature has been ques- 

 tioned by many who assume that the bacteria are 

 the primary agents in causing the intestinal lesions 

 and that the amebae are only incidental or second- 

 ary factors. Many others, and particularly Mus- 

 grave and Clegg, consider that amebas have essen- 

 tial pathogenic properties and are the primary 

 agents in producing amebic dysentery. By the 

 feeding of encysted cultures grown with other or- 

 ganisms, Musgrave and Clegg reproduced the dis- 

 ease typically in many monkeys. In one instance 

 the amebae were fed in conjunction with cholera 

 vibrios; typical dysentery developed and during 

 the course of the disease the vibrios disappeared 

 from the stools. The vibrio alone proved to be 

 non-pathogenic when fed to monkeys, and on this 



