355
sudden lowering of the blood-pressure at 2h. 17m. 50s. and at 2h. 48m. 25s. ; the animal was
quite out of chloroform at these times, and it was not even being administered. Chloroform
administration was commenced with plenty of air and regular breathing at 2h. 18m.
35s. The gradual and regular fall of blood-pressure is very well shown in this
observation. The breathing stopped at 2h. 24m. 5s., and electrical irritation of the vagus
was begun at 2h. 24m. 15s., and continued until 2h. 25m. 10s. The only apparent effect
of the vagus stimulation was to slow the heart without lowering the blood-pressure. Artificial
respiration was not employed, and the animal recovered rapidly.
" Ludwig II.-In this observation chloroform administration was commenced simul-
taneously with electrical irritation of the vagus at 2h. 35m. 50s. The blood-pressure fell
suddenly almost to zero. This was followed by a pause and then two slow beats of the heart.
The pulse trace then slowly returned, and the pressure gradually rose to a little more than
half its former height, and then gradually fell again as it does in normal chloroform admin-
istration. The pulse remained slow. The respiration ceased entirely at 2h. 37m. 15s. The
vagus irritation, which was begun at 2h. 35m. 50s., was continued until 2h. 39m. 5s., when it
was stopped, and normal breathing at once recommenced without. any further steps being
taken to revive the animal. In this observation the effect of the vagus irritation. was to
suddenly lower the blood-pressure and to slow the pulse. The stoppage of the respiration is
to be particularly noted and kept in mind with reference to the next observation in
Ludwig III.
" In Ludwig III, chloroform inhalation with normal breathing was commenced at 2h. 53m.
35s. The blood-pressure fell gradually and regularly. The breathing stopped at 2h. 55m. 45s.,
but it was not recorded till 2h. 56m. Os. in order to make sure that it had quite stopped.
Electrical irritation of the vagus was commenced at 2h. 56m. 10s, and continued till 2h. 57m.
25s. The blood-pressure fell suddenly and remained low, with slow action of the heart for
one minute and fifteen seconds. The animal recovered spontaneously without artificial re-
spiration or any other treatment. (If Ludwig IV is now examined, it will be seen that
the chloroform observation of Ludwig III was repeated. - When the breathing stopped,
the animal was left entirely alone and he died.) The question that arises about the
animal's recovery in the experiment recorded in Ludwig III is, what was the
recovery due to ? It must be noted that the vagus was not divided. The visible
effect of the irritation of the entire vagus was to lower the blood-pressure which
was already dangerously (?) low, and slow the pulse. It might be objected that the
irritation of the uncut vagus stimulated the respiratory centre, and so saved the animal's
life. But if this might be said about Ludwig III, it might equally fairly be sail about
Ludwig II that the irritation of the vagus at 2h. 35m. 50s. saved the dog's life by stopping
the respiration, which would be absurd, as the irritation of the vagus cannot be a saf e guard,
or save life, by stopping the respiration in one case and exciting it in another. If lowering
the blood-pressure were dangerous and due to weakening of the heart, it is clear that the stimu-
lation of the vagus at 2h. 56m. 10s., when the animal's breathing had stopped and the pressure
was already perilously (?) low, was the very worst and most dangerous expedient we could