CULTIVATION 645 



name E. minuta. Other observers, however, consider that it is simply a 

 variety of E. tetragena. Noc, working in Cochin-China, cultivated 

 amoebae from the intestines in dysentery, from liver abscesses and from 

 drinking water, and found that they all had the same characters. The 

 process of encystment was different from that described by Schaudinn, 

 the whole cell becoming enclosed by the cyst. In addition to the 

 ordinary method of fission, it formed numerous small cells or merozoites 

 by a process of budding within the protoplasm ; these afterwards 

 becoming free. Greig and Wells, working in Bombay, have cultivated 

 and described an amoeba closely similar to that of Noc ; and it is of 

 interest to note that they also obtained the same organism from liver 

 abscesses, from the stools in dysentery, and also from drinking water. 



Cultivation. Various attempts have been made to cultivate 

 the amoeba of dysentery, and Kartulis considered that lie obtained 

 growth in straw infusions. Within recent years cultures of 

 amoeboe in association with various bacteria have been obtained 

 on agar media by various workers, e.g., Lesage, Musgrave and 

 Clegg, Noc, and others. For this purpose a plain agar without 

 peptone is used. 



The medium of Musgrave and Clegg has the following composition : 

 Agar ....... 20 grms. j 



Sod. chloride 0'3-0'5 grm. 



Extract of beef '3-0 '5 grm. 



Distilled water 1000 c.c. 



It is prepared in the usual way and is made 1 per cent, alkaline to 

 phenol-phthalein. 



The presence of bacteria seems to be essential for the growth 

 of the amoebae, and it is found that some species favour growth 

 whilst others act prejudiciously ; amongst the former may be 

 mentioned the sp. cholerae, b. subtilis, and various members of 

 the coli group, though organisms from a great variety of sources 

 have been found to be equally efficient. 



In such cultures, which are most conveniently made in Petri 

 dishes, the stages of growth and encystment of the amoebae can 

 be readily studied ; many species nourish best at a temperature 

 of about 25 C. Although cultures without bacterial growth 

 have not been obtained, means have been devised to ensure 

 that only one species of amoeba is present. For this purpose 

 Musgrave and Clegg select, by means of a low-power objective, 

 an amoeba well separated on the agar plate, place it in the 

 middle of the field, then swing into position a high-power 

 objective, and, having ascertained by means of it that the amoeba 

 is still there, lower the point of the lens on to the agar. By 

 this means the amoeba may have been picked up, and it may 

 then be transferred to a fresh plate. Lesage is the only observer 



