A SIMPLE METHOD OF DEMONSTRATING 

 THE EFFECT OF HEAT AND POISONS 

 UPON THE HEART OF THE FROG. 



(From the Journal of Anatomy and Physiology, vol. x, 1876.) 



The fact that heat accelerates and cold retards the pulsations of 

 the heart, is one of such fundamental importance, both in regard 

 to a right understanding of the quick pulse, which is one of the 

 most prominent symptoms of fever, and to a correct knowledge 

 of the proper treatment to apply when the heart's action is fail- 

 ing, that for the last year or two I have been accustomed to 

 demonstrate it as a lecture experiment. The apparatus I use is 

 exceedingly simple, but it answers its purpose well, and by its 

 means the pulsations of the frog's heart can be readily shown to 

 several hundred persons at once. I exhibited it at the meeting 

 of the British Medical Association in London more than two 

 years ago, and a description of it appeared in the British Medical 

 Journal for August 23, 1873 ; but as I have reason to believe 

 that few physiologists have seen either the instrument or its 

 description, it may not be amiss to say a few words regarding it 

 here. It consists of a piece of tin plate or glass 3 or 4 inches 

 long and 2 or 3 wide, at one end of which an ordinary cork cut 

 square is fastened with sealing-wax in such a manner that it 

 projects half an inch or more beyond the edge of the plate. 

 This serves as a support to a little wooden lever about 3 inches- 

 long, a quarter of an inch broad, and one-eighth of an inch thick. 

 A pin is passed through a hole in the centre of this lever, and 

 runs into the cork so that the lever swings freely about upon it 

 as on a pivot. The easiest way of making a hole of the proper 

 size, is simply to heat the pin red hot, and then to burn a hole 

 in the lever with it. To prevent the lever from sliding along 

 the pin, a minute piece of cardboard is put at each side of it, 

 and oiled to prevent friction. A long fine bonnet straw or 



