646 AMCEBIC DYSENTERY 



growth in straw infusions. Within recent years cultures of 

 amoebae in association with various bacteria have been obtained 

 on agar media by several 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. 



Sod. chloride . . . . ■%-•§ grm. 



Extract of beef . . '3- - 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. cholerse, 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 flourish 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. By such and other methods 

 various amoebae have been cultivated from water, vegetables, etc., 

 and their process of encystment has been observed. But it has 

 not been conclusively shown that these have pathogenic pro- 

 perties, and on the other hand there is no satisfactory proof that 

 either the E. histolytica or the E. coli has been obtained in 

 culture outside the body. 



Distribution of the Entamoeba. — As already stated, they are 

 usually found in large numbers in the contents of the large 

 intestine in tropical amoebic dysentery. They also, however, 

 penetrate into the tissues, where they appear to exert a well- 

 marked action. In this disease the lesions are chiefly in the large 

 intestine, especially in the rectum and at the flexures, though 



