206 FAMILY: AMCEBIDtE 



by Chatton (1917, 1918rf). This may be accomplished by injections 

 per anum or by feeding with cysts per os. In these animals dysenteric 

 symptoms do not appear, but large tumours develop about the caecum, 

 and these are found to consist of overgrowths of the tissues due to the 

 amoebae, which grow and multiply within them. Huber (1909) claims to 

 have produced a chronic ulceration of the caecum in rabbits by feeding 

 them with cysts, while Lynch (1915) and Brug (1919a) claim to have 

 infected rats. Kessel (1923a) states that he has infected rats and mice 

 with E. histolytica. He finds (1923) that natural amoebic infections of 

 these animals can be excluded by the examination on two successive days 

 of faeces obtained after the administration of a purge in the form of stale 

 bread soaked in magnesium sulphate solution. To such animals cysts 

 of E. histolytica were given. The infections produced are of a chronic 

 nature, and persist for months. Free forms, as well as characteristic 

 cysts, could be obtained in the faeces of the animals after giving them 

 magnesium sulphate. The infection was handed on from rat to rat. 

 Chiang (1925) has also infected rats. The amoebae from the experimental 

 rats, as well as a naturally occurring rat strain {E. histolytica var. murina), 

 gave rise to typical infections when inoculated to kittens. Clean rats 

 kept with infected ones contracted an E. histolytica infection. 



Attempts which have been made to infect monkeys have been incon- 

 clusive, owing to the fact that these animals are liable to natural amoebic 

 infections due to two species of amoebae which are very similar to E. histo- 

 lytica and E. coli. These animals suffer from amoebic dysentery, and 

 even amoebic abscess of the liver, as pointed out by Eichhorn and Gallagher 

 (1916) and others (see p. 226). 



CULTIVATION. — Many attempts have been made to cultivate E. histo- 

 lytica in artificial media, but the only successful results are those of Cutler 

 (1918) and Boeck and Drbohlav (1925). Other observers have cultivated 

 only coprozoic amoebae. Cutler used two media. 



The first was made as follows: The entire contents of an egg were 

 broken up by shaking in a glass bottle with beads. To the broken-up 

 egg 300 c.c. of distilled water were added, and mixture was effected by 

 shaking. The fluid was then brought gradually to the boiling-point in 

 a water bath, and kept at this temperature for half an hour. During the 

 heating the mixture was shaken, so that a fluid was obtained in which 

 minute egg particles were suspended. It was then distributed in quanti- 

 ties of 5 c.c. in test-tubes and autoclaved. Before use a few drops of 

 blood were added to each tube. 



The second medium was prepared by boiling 500 c.c. of human blood- 

 clot for an hour in a litre of water. To the filtrate was added 0-5 per 

 cent, sodium chloride and 1 per cent, peptone. The fluid was then tubed 



