ON THE HEART, BLOOD-PRESSUIIE AND BLOOD. 479 



tlie whole head. In one of us (Brunton) it was several times 

 accompanied by vomiting. It has been said by some that con- 

 tinned use of nitro-glycerine makes the person more sensitive, 

 but in one of us (Tait) the contrary seemed to be the case, as 

 the headache was only suffered from during the first w^eek of 

 the investigation. None of the poison was taken by the mouth, 

 and, as it is non-volatile, the amount taken in by the lungs must 

 have been infinitesimal. lb is possible that, as some writers 

 have supposed, a little of it was absorbed by the skin, but the 

 quantity thus taken into the system must have been excessively 

 minute. 



Action on the Heart. — When the excised heart of a frog is 

 put into 10 cubic centimetres of a '75 per cent, salt solution, 

 and two drops of a 10 per cent, solution of nitro-glycerine in 

 alcohol are added, the heart begins to beat more and more 

 slowly, and gradually ceases altogether. A similar quantity of 

 alcohol, added to the same amount of salt solution, had no 

 action on a heart immersed in it. In one instance, after the 

 addition of nitro-glycerine, we observed a slight quickening 

 before the beats became slow. 



Two cubic centimetres of a 10 per cent, solution of nitro- 

 glycerine in alcohol injected into the jugular vein of a cat 

 stopped the cardiac pulsations entirely in 13 seconds. One 

 cubic centimetre in another experiment greatly quickened the 

 pulse. The power of the vagus over the heart appears to be 

 diminished, as irritation of its trunk had less effect upon the 

 heart after injection than before. 



Action on the Blood-pressure. — Nitroglycerine diminishes the 

 blood-pressure considerably, but its power to do so is very much 

 less than that of nitrite of amyl. 



Action on the Blood. — The blood of animals poisoned by 

 nitro-glycerine is of a chocolate colour, even in the arteries. 

 When blood is shaken up with nitro-glycerine solution, it 

 acquires a chocolate colour, though slowly. In this respect 

 nitro-glycerine agrees with nitrites, which also cause the blood 

 to assume that colour. 



With the spectroscope at our disposal, however, w^e were 

 unable to discern any difference between the spectrum of blood 



