go Dr. Parry on a Case of nervous Affection. 
rapidity or intensity of thought, which constituted delirium, 
immediately ceased, and gave place to other trains of a healthy 
kind ; head-ach and vertigo were removed, and a stop was 
put to convulsions, which the united strength of three or four 
attendants had before been insufficient to counteract. 
That this extraordinary effect was not that of mere pressure, 
operating as a sort of counteracting stimulus, was evident : 
for the salutary effect was exactly proportioned to the actual 
pressure of the carotid itself, and did not take place at all, if, 
in consequence of a wrong direction either to the right or left, 
the carotid escaped the effects of the operation. 
This view of the order of phoenomena was, in reality, very 
conformable to the known laws of the animal oeconomy. It 
is admitted, that a certain momentum of the circulating blood 
in the brain, is necessary to the due performance of the func- 
tions of that organ. Reduce the momentum, and you not 
only impair those functions, but, if the reduction go to a cer- 
tain degree, you bring on syncope, in which they are for a 
time suspended. On the other hand, in nervous affections, 
the sensibility and other functions of the brain are unduly in- 
creased ; and what can be more natural than to attribute this 
effect to the contrary cause, or excessive momentum in the 
vessels of the brain ? If, however, this analogical reasoning 
has any force in ascertaining the principle, I must acknow- 
ledge that it did not occur to me till twenty years afterwards, 
when a great number of direct experiments had appeared to 
me clearly to demonstrate the fact. 
From various cases of this kind, I beg leave to select one 
which occurred to me in the month of January, 1805. 
Mrs. T. aged 51, two years and a half beyond a certain 
