ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 101 



circulation and rotation of protoplasm and the movement of the chloro- 

 phyll bodies within the cells of the leaf of Elodea ; the circulation of 

 the blood in the web of the frog's foot and in the tail of the goldfish. 

 The lecturer also exhibited microbioscope pictures of Hydra viridis, 

 various birds, beasts, and reptiles in motion, and of the life and work of 

 the wood ant. 



B. Technique.* 

 (1) Collecting' Objects, including- Culture Processes. 



Endo's Fuchsin Agar.f — K. Fiirntrat finds that when fuchsin 

 solution has been decolorised by sodium sulphite, the colour can be 

 restored by the addition of the smallest quantity of either a mineral or 

 organic acid, but the colour can again be removed by a further addition 

 of sodium sulphite or by excess of acid ; the colour can also be restored 

 by the addition of formalin, but can only be removed again by excess 

 of sodium sulphite ; the solution decolorised by sodium sulphite regains 

 its colour on warming, but on cooling the colour is again lost ; fuchsin 

 solution is decolorised by a relatively large addition of acid, but if 

 mineral acid is used the colour is not restored on heating. 



Endo's medium consists of lactose nutrient agar coloured red with 

 fuchsin, and to which sufficient sodium sulphite has been added to render 

 it colourless when cool. On this medium the colonies formed by 

 B. typhosus are small and colourless, whereas in the same period of time 

 those formed by B. coli are large and of a deep red colour, which is 

 diffused in the medium ; after 15 hours growth these organisms may be 

 differentiated. The author finds that single surface colonies of 

 B. typhosus after 36 hours exhibit a faint pink colour, especially if the 

 medium is more than two weeks old ; that the colonies of B. coli and the 

 surrounding medium begin to decolorise after 24 hours, and in the 

 course of the next day all colour is lost, especially with grouped colonies, 

 the isolated colonies retaining the red colour for a much longer time ; 

 the colonies of B. coli lose their colour more quickly if colonies of 

 B. typhosus are grown simultaneously on the same plate. 



The author applies the results of his observation on the chemistry 

 of fuchsin to explain these bacteriological phenomena. 



Modification of Endo's Medium.^ — W. Gaehtens has modified the 

 fuchsin agar medium devised by Endo for the differentiation of 

 B. typhosus and B. coli by the addition of caffein, which hinders the 

 growth of B. coli. He gives full details of the method for preparing 

 his medium. After many trials of various doses of caffein and of 

 degrees of alkalinity, he finds that the addition of ' 33 p.c. of chemically 

 pure crystalline kaffein to Endo's medium of an alkalinity of 1 ' 5 p.c, 

 normal sodium hydrate, (?+l'5N) serves best to considerably hinder 



* This subdivision contains (1) Collecting Objects, including Culture Pro- 

 cesses ; (2) Preparing Objects ; (3) Cutting, including Imbedding and Microtomes ; 

 (4) Staining and Injecting ; (5) Mounting, including slides, preservative fluids, &c. ; 

 (6) Miscellaneous. 



t Centralbl. Bakt. Orig., xxxix. (1905) p. 487. J Tom. cit., p. 634. 



