750 



THE AMOEBAE 



The protoplasm is streaked with blue and the nucleus is red or 

 violet. 



D. Borrel's method. (vide Coccidia, Chap. LVII.) 



Cultivation. 



It has not yet been definitely established that cultures of the Amoeba histo- 

 lytica have been grown. Lesage, who has obtained cultures with which he 

 has caused dysentery in young cats, is of opinion that these cultures owe 

 their pathogenic properties not to the amoebse which have multiplied and 

 are probably saprophytic species, but to the Amoeba histolytica, which has 

 not multiplied but has retained its vitality. In any case cultures of intestinal 

 amoeba? can only be obtained by growing them symbiotically with bacteria 



and it would seem that they require 

 living bacteria for food (Frosch. 

 Mouton, Musgrave and Clegg, and 

 others). The medium should be 

 either a very feebly nutritive agar 

 prepared with agar which has been 

 washed for a long time (Lesage) or 

 a similar medium containing a very 

 small quantity (O03-0'05 per cent.) 

 of meat-extract and made alkaline. 

 Kartulis obtained cultures by sowing 

 small amounts of stools in an infusion 

 of straw, but the amoebae only grew 

 provided that the flasks were not 

 plugged even with wool. These experi- 

 ments however, as Schubert pointed 

 out, are valueless as evidence that the 

 amoeba can be cultivated outside the 

 body because the amoebae found in the 

 straw infusion were simply impurities 

 from the dust in the air. 



Musgrave and Clegg isolated in- 

 testinal amoebae by sowing stools on 

 agar plates previously sown with bacteria, for preference bacteria isolated from 

 the intestine of the patient. These amoebae, which Musgrave and Clegg 

 found in water, in soil and on vegetables in the neighbourhood of Marseilles, 

 would appear to be saprophytic species. Musgrave and Clegg are of opinion 

 that all intestinal amoebae may become pathogenic. 



Lesage obtained cultures of amoebae from 7 out of 30 cases of tropical dysentery. 

 He sowed a little of the intestinal mucus either fresh or after it had been dried 

 (encysted amoebae) on the surface of agar plates. After incubating for a few days 

 at 18-25 C. small amoebae were found at the points where the material was sown 

 and were transferred to a fresh agar plate in such a manner as to be a little distance 

 away from a colony of a paracolon bacillus. Sub-cultures were again made as 

 soon as the amoebae reached the colony of bacteria and after sub-cultivating in 

 this fashion several times a mixed culture of amoebae and paracolon bacilli was 

 obtained. Cultures obtained in this way are very long-lived : Lesage kept his 

 amoebae in culture for 2 years and sub-cultured them 66 times ; the amoeba lives 

 from 4^5 months in one culture while the cyst retains its vitality for at least 68 

 months. 



More recently Lesage has found that his cultures were merely cultures of sapro- 

 phytic amoebae and this would also appear to be the case with the cultures he 

 obtained by sowing dysenteric stools on leucocytes of guinea-pigs, rabbits, cats 

 and man. 



FIG. 354. Amoeba histolytica in recent stools. 

 The figures represent the different forms assumed 

 by the parasite when observed every 15 seconds. 

 The endosarc contains a nucleus and three in- 

 gested red cells. (After Jiirgens.) 



