The Action of Tannin, &c. By H. J. Waddington. 187 



opaque. It does not appear to kill tlie Paramsecium itself — at 

 least for some little time, unless the solution is very strong, as the 

 rhythmical contraction and expansion of the contractile vesicles may 

 be still observed. In the most successful observations it is probable 

 that the tannin solution has been of sufficient strength to act upon 

 the very delicate cilia, and, as it were, to paralyse them ; while it 

 has not been of sufficient strength to kill the animal outright. In 

 the face of the accepted theory that ciliary motion is involuntary, 

 it would be incorrect to say that the tannin acts upon the cilia in 

 such a manner as to render them beyond the animal's control ; but 

 the cilia are certainly rendered inert, while the functions of the 

 animal are but little impaired for a time. 



The form of tannin which I have found most convenient to use 

 is the glycerole of tannin, which is merely tannin dissolved in 

 glycerine in the proportions of one part to four. It is a thick, 

 viscid body, very stable, easily miscible with water, and conse- 

 quently very manageable, as the quantity added to the water under 

 examination can be well adjusted, and the action is more satisfac- 

 tory than it would be if a solution of nearly the same specific gravity 

 as water were used. Tannin in alcohol is not advisable on account 

 principally of the repellent action between the alcohol and the 

 ■\vater. 



That the immediate action of the tannin in moderate quantity is 

 not to kill the Paramsecium is, I think, apparent from the fact 

 that Infusoria much more minute than Paramsecia seem to be little 

 affected by it. I have constantly seen these become entangled in 

 the cilia of Paramsecium that had been rendered motionless by 

 tannin, and extricate themselves after a time apparently little 

 affected by it. But such Infusoria have not possessed cilia of the 

 same character as Paramsecium. On Stylonychia the tannin 

 does not appear to have so decided an action, and whenever 

 the cilia take the form of setse the Infusoria seem much more 

 capable of resisting its paralysing action, the peculiar jerky motion 

 of the setae being kept up for some time. 



I have made the remark that I think no correct ideas have 

 hitherto been held as to the size and quantity of the cilia; at 

 any rate, I have never seen any drawing, or read any description of 

 Paramsecium, as it is observed after the treatment by tannin. That 

 the appearances observed are really cilia may be easily verified by 

 the action of osmic acid, which kills the Paramsecium at once, 

 and renders the cilia visible, but not to the extent that they are so 

 rendered by the tannin. 



I may also make allusion to the action of another chemical body 

 on Infusoria, and to the advantages it seems to possess in micro- 

 scopical research. This body is sulphurous acid, or, in the form in 

 which I have found it most useful, solution of sulphurous oxide in 



