XXI] PATHOGENIC ORGANISMS 543 



cotton-wool. The infusion is made while the water is still 

 tepid. After half an hour the infusion is filtered into a 

 fresh sterile flask, plugged with sterile cotton-wool, the access 

 of air being limited as much as possible. This is effected 

 by keeping the cotton-wool in the mouth of the flask around 

 the end of the glass filter. The filtered fluid is of a slightly 

 yellowish-green colour, and is almost neutral and limpid. 

 A small quantity is withdrawn with a capillary glass pipette 

 freshly drawn out, and from this several test-tubes containing 

 sterile nourishing material (peptone solution, broth, Agar- 

 Agar and peptone) are inoculated ; and from the same 

 pipette, and at the same time, several eyeballs of healthy 

 rabbits are inoculated, by placing a drop or two of the 

 infusion under the conjunctiva bulbi. The test-tubes are 

 placed in the incubator and kept there at 35° C. After 

 twenty-four hours all eyeballs are intensely inflamed, the 

 eyelids closed and swollen, and a large amount of purulent 

 secretion is present in the conjunctival sac, but all the test- 

 tubes remain perfectly limpid ; no growth has made its 

 appearance, and they remain so. 



In a second series the infusion prepared in the above 

 manner is used fifteen minutes after it is made and used as 

 above, for inoculation of test-tubes and eyeballs. The fluid 

 in the test-tubes after incubation remains limpid, the eyeballs 

 all become inflamed. In both series the amount of fluid 

 inoculated into the test-tubes is more than twice as great 

 as that injected into the eyeballs. From this it is quite 

 clear that the fluid used for inoculation of the test-tubes was 

 barren of any micro-organisms, and nevertheless it possessed 

 a powerful poisonous principle. I do not mean to say that 

 the infusion as a whole contained in the flask contains no 

 organisms, but that the small quantity of the fresh infusion 

 that was used for the inoculation of the test-tubes and eyeballs 



