1905-6.] Standardising Suprarenal Preparations. 
169 
In an experiment on a cat, the amount of adrenalin which pro- 
duced a moderate rise of pressure (’03 mg. in 1 c.c.) was combined 
with grain of nitroglycerin, and a result very similar to that 
given with the smaller dose in rabbits was given (fig. 4). 
The preliminary rise of adrenalin is again inhibited by the action 
of the nitroglycerin, and the normal pressure level is rapidly reached. 
It is interesting to note that although the adrenalin must be used 
in strong solutions in order to effect the blood pressure in the cat, 
nitroglycerin apparently acts in very much the same way in the 
cat as it does in the rabbit. This also tends to prove that adrenalin 
Fig. 4. To show the neutralising effect of nitroglycerin and adrenalin on the blood 
pressure of the cat, ’03 mg. of adrenalin against 0’6 mg. of nitroglycerin.* 
and a nitrite act independently but in opposite directions — in other 
words, that the antagonism is what might be called dynamic rather 
than chemical. 
Of these two methods employed for the combination of nitrite 
and adrenalin, that of estimation by the blood pressure is more 
satisfactory. The action of adrenalin when perfused through the 
peripheral circulation is of considerable duration, while a return to 
the normal is more rapid with a nitrite. On long-continued per- 
fusion then, although at first an antagonism is established, the 
adrenalin effect ultimately appears on discontinuing the perfusion. 
The power of the cells to react to the stimulus of nitrite is more 
readily exhausted ; then the adrenalin effect is seen. 
* Top line is the respirations. 
