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Physiology. — “The negative-inotropic influence of the nervus 
vagus on the heart’. By Prof. To. W. ENGELMANN. 
The weakening influence of the vagus on the contractions of the 
heart, discovered and studied by Nver in Professor DonpErs’ labo- 
ratory, has been more closely examined by the speaker with the 
aid of the method of suspension and the pantokymographion. 
Speaker’s experiments have mostly been made on the atria of the 
frog’s heart, in which the above-named action can be examined 
most easily. 
It can here be provoked by direct irritation of the vagus-root and 
the vagus-origines in the brain, as well as through direct irritation 
of the atria, eventually of the sinus or ventricle-base (irritation of 
the intracardial vagusbranches), also by reflexaction from different 
parts of the body, especially so from the intestines. Generally 
speaking the action is in all cases the same in quality; it is also 
a case of indifference whether the heart beats spontaneously or 
whether the ventricle is brought to regular beating, antiperistaltic- 
ally, by artificial irritation of the ventricle. : 
The effect is furthermore independent of eventual other, chrono- 
tropic, dromotropic or bathmotropic actions of the vagus-irritation, 
although often combined with it. 
It shows itself in the following manner after one single induction- 
shock causing momentary irritation: After a very short latent stage 
the diminution in size and length of the contractions commences, 
which very soon reaches its maximum; after that the systoles gra- 
dually become more considerable and of longer duration. 
Intensity and duration of the whole process rise within ample 
limits with the strength of the irritation. 
The duration of the period of increasing debility is comparatively 
constant; during the experiments of the speaker, taken at an 
ordinary temperature and retained circulation, it proved to be 3—4 
sec.; the lowest value was found with the strongest irritation. The 
latency lasts in the most favourable case less than 0.5". The stage 
of the diminishing process can be prolonged for more than one 
minute. The weakening can lead temporarily to the entire cessation of 
the contractility. 
The phase of the period of the heart in which the irritation takes 
place, has no perceptible influence. A refractory stage is therefore 
also wanting. Through superposition of cardiograms obtained by fre- 
quently repeated vagus-irritation of equal strength and duration, on 
the same absciss, the turning cylinder of the kymographion having 
