16 PRACTICAL PARASITOLOGY 



water for several hours (it may be left in all night) at a gentle heat, 

 and then repeatedly sterilizing the resulting liquor. 



Another very useful medium is prepared from carragheen. This 

 medium is particularly useful in laboratories which are not provided 

 with the sterilizing appliances necessary to bacteriological work. Its 

 value is increased by the fact that, where the material employed is 

 unaltered excreta, it is possible successfully to cultivate Amoebae upon 

 preparations of carragheen which have not been subjected to rigorous 

 sterilization. Five to six grains of dried carragheen is washed in 

 1 per cent, soda solution and then boiled for half an hour in 100 c.cm. 

 tap water. 1 The medium should be filtered through a clean cloth and 

 when cold it will be ready for use. Colonies of mould-fungi or foreign 

 bacteria should immediately be destroyed with a hot platinum needle. 



It must be borne in mind, however, that not all Amoebae can be 

 cultivated upon solid media, and that the varieties which are parasitic 

 in mammals have never been successfully grown outside the tissues 

 of their host. I have, however, succeeded in cultivating on Frosch's 

 agar medium, not Amoebae only, but also Flagellates, obtained from 

 the scum on hay or earth infusions. 



Amoebae are best cultivated in Petri's glasses. If the organisms are 

 present in large numbers in the inoculation mass, they may be seen 

 a few hours after inoculation following the bacteria and spreading 

 out round the point of inoculation. They will be found, not only 

 upon the surface, but within the substance of the medium, which, to 

 facilitate observation under the microscope, should cover the bottom 

 of the Petri glass in a very thin layer. In the course of the next 

 few days the Amoebae will increase in numbers and alter their 

 distribution; cysts will form, also in largely increasing numbers. 

 The cultures will remain active over a period varying from several 

 weeks to several months. 



There is yet another way of studying the living Amoeba. A drop 

 of the fluid which contains the organisms is placed upon a cover-glass, 

 which is then turned, face downwards, upon a glass slide. The 

 preparation should be allowed to stand for about ten minutes in order 

 that the Amoebae, which have contracted into balls on being disturbed, 

 may again throw out processes. The movements may now be observed, 

 and these will be found to vary considerably in different species. The 

 A. Umax, frequently found in infusions of straw, assumes a ribbon-like 

 form as it flows forward; other Amoebae, as for instance A. proteus, 



1 Cf. M. Schubert, " Ueber die ZUchtung der Ainoben auf festen Nahrboden," 

 Hygien. Bundschau, 1897, No. 2 ; also E. Vahlkampf, " Beitrage zur Biologic und 

 Entwickelungsgeschichte von Amoeba Umax einschliesslich der Zuchtung auf 

 ktinstlichen Nahrboden," Arch. f. Protistenkunde, vol. v, 1905, pp. 167-220. 



