ACTION ON INFUSORIA. 21-3 



cilia, in white blood-corpuscles, or in those minute bodies — 

 bacteria and vibriones — to which attention has of late been so 

 much directed, and which, despite their minuteness, possess so 

 much importance from their power of producing fermentation 

 and decomposition in dead organic matter, and not improbably 

 of causing disease in living beings. For the purpose of study- 

 ing it in Infusoria, we prepare an infusion of hay some days 

 before we wish to experiment, and a solution in water of the 

 drug wdiich we wish to investigate. We then heat a piece of 

 glass tubing in the middle, draw it out and cut it across, so as 

 to obtain two little pipettes, which will deliver drops of nearly 

 equal size.. From one of these we let fall a drop of infusion of 

 hay on a glass slide, and examine it under a low power of the 

 microscope without a covering glass. We then let fall a drop 

 of the solution of our drug upon it, mix the two drops well with 

 a glass rod, and again examine them microscopically to see 

 whether or not the infusorial animalcules are still moving. If 

 they be moving, and continue to do so for some time, we pre- 

 pare a stronger solution of the drug; but if they have com- 

 pletely stopped when we looked, we make a weaker one, and 

 again mix a drop with one of hay infusion, repeating the experi- 

 ment till we have got a solution of such a strength that a slight 

 movement of the animalcules can be observed just after mixing 

 the drops, but ceases almost immediately, and cannot be brought 

 back by adding water. We can then compare the action of 

 different drugs by observing of wdiat strength the solution of 

 each must be, in order to produce precisely this effect. 



Professor Binz of Bonn has found in this way that certain 

 substances, such as common salt, chlorate, chloride and bro- 

 mide of potassium, alum, &c., appear to stop the movements of 

 Infusoria by altering the amount of water which they contain, 

 as strong solutions cause them to shrivel at first, and then to 

 swell up and become motionless. Weaker ones make them 

 swell likewise ; but their effect at first is different, as they do 

 not shrivel up the animals, but, on the contrary, render their 

 movements more lively. 



Other substances kill them in a way which we do not under- 

 stand, stopping the movements at once without producing any 



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