98 
BRITISH ASSOCIATION.— 1835 . 
On the Differential Pulse. By Dr. M’Donnell. 
Dr. M’Donnell’s paper began with a description of what he terms 
“ the Differential Pulse,” and with proofs of his claim to priority in 
ascertaining it in 1784. The observations which succeed related to 
the following subjects. 
The influence of disease and of particular remedies upon the 
pulse, with a reference to the effect of posture on the number of 
beats; the absence of this phenomenon in quadrupeds, owing to 
their natural vessels being horizontal in both the lying and standing 
posture; certain cases of health and disease, in which the maximum 
and minimum of this variation are found ; the methods to be pursued 
for investigating the number of the pulse in wild and ferocious ani¬ 
mals as deducible from their respirations; the proportion between the 
stops, pulses, and respirations in man and quadrupeds in active ex¬ 
ercise ; observations made at a depth of 26 feet in a diving-bell, 
which corroborate the views of Sir David Barry and Dr. Carson on 
the moving powers in the circulation; proofs that barometrical va¬ 
riations have no influence upon the pulse or breathings. 
Part 2.—On the limitations of the doctrine of the “ Differential 
Pulse of stationary or permanent pulses; observations made on 
the pulses of children before and after their having respired; of the 
acceleration of the pulse after birth; observations on quadrupeds 
with respect to this; supposition that the foetus remains before 
birth in the state of the cold-blooded animals; of the final cause of 
this peculiarity; of the cause of the stethoscopic sounds of the 
foetal heart being very rapid, although the pulse in the funis be slow; 
an account of an experiment made by a watch ticking under water; 
of the remarkable strength of the foetal pulse as felt in the chord; 
of the absorption of the blood in the chord into the system of the 
foetus after delivery; and the inference from this in favour of the 
view's of Sir David Barry and Dr. Carson respecting the suction pow r er 
of the thorax as influencing the circulation. 
On some hitherto unobserved Differences in the Effects of Accumu¬ 
lations of Liquids or of Air within the Cavity of the Thorax. By 
Dr. William Stokes. 
In this communication Dr. Stokes pointed out a new source of 
diagnosis, namely, the paralysis of certain of the respiratory muscles 
which results from their vicinity to an inflamed tissue. 
The excitement of muscular tissue produces at first active con¬ 
tractions, as shown by pain and spasm ; but when still longer conti¬ 
nued, the contractility is either lost or greatly diminished. These 
effects may be produced in a threefold manner: 1st, by direct ir¬ 
ritation of the muscular tissue; 2ndly, by the contiguity of muscle 
to an inflamed tissue; and 3rdly, by irritation in the cerebro-spinal 
centres or nerves. Of these, the first have been recognised in cer¬ 
tain thoracic diseases; but the second, or the paralysing effect, has 
been hitherto neglected. 
