INACTION OF DIGITALIS IN PNEUMONIA. 211 



the alteration of temperature, and, as it were, announced the 

 occurrence of the latter. 



Here, then, at the very beginning of fever, we have a quick- 

 ening of the pulse which cannot be due to temperature. It 

 might be produced by stimulation of the motor ganglia in the 

 heart itself by some cause yet unknown, by stimulation of 

 the quickening centres in the brain and cord, or by dimi- 

 nution of the power of the vagus, either through some impres- 

 sion made directly on the brain, or indirectly through some 

 change occurring in the arteries and altering the blood pres- 

 sure. The first cause seems very unlikely, and it is more 

 probably due to either the second or third, but this must be 

 decided by future investigations. On this point I have made 

 no experiments, my attention having been attracted rather to 

 the effect which high temperatures in fever would have upon 

 the vagus, and to the way in which this might modify the 

 action of the remedies then employed. 



Thomas* found that digitalis sometimes had no action on the 

 pulse when given in pneumonia, and as digitalis acts chiefly 

 through the vagus it seemed to me possible that its want of 

 action might be due to paralysis of the inhibitory apparatus in 

 the heart through which the vagus acts upon it. 



This appeared all the more probable since Schelske and 

 Cyon had found that a high temperature paralysed it in 

 the heart of the frog, and the rapid increase in the pulsations 

 noticed by Liebermeister between the temperatures of lOS'S" 

 and 107'6° F., seemed to indicate that the same thing occurred 

 in the mammalian heart. In order to test the truth of this 

 supposition, I performed the Experiments I, III, IV, V, and 

 VIII, which are given in detail below. 



The animals were narcotised, the vagi exposed, and their 

 power tested by irritating them by an induced current from one 

 of Du Bois Eeymond's coils. The temperature of the animal 

 was then raised, and the power of the vagus tested from time 

 to time with a current of the same strength as that used at first. 

 From these experiments, and especially from 'No. VIII, it will 

 be seen that as the temperature was raised and the pulse quick- 



» Thomas, Arch./. Reilk., yi, 4, p. 329, 1865. 



p 2 



