Volltext: Elements of Physiology

CAJJSja OP THE heart’s AÇTI0N. 
tion; for when they can breathe neither by the lungs nor by the skin, 
namely, when they are immersed in pure hydrogen, frogs live more 
than twelve hours, as I have myself witnessed. Though here it 
must be remembered, that one great object of respiration is the 
removal of carbonic acid from the blood, and that this is fulfilled, in 
a great measure, when frogs are confined in hydrogen gas. The 
final cessation of the heart’s action, in cases where respiration is 
suspended, may indeed depend chiefly on the change which ensues 
in the nervous system when it no longer receives red blood. 
The disturbance of the circulation, after interruption of the respira¬ 
tion in the higher animals, is certainly not produced by the collapse 
of the lungs, the experiments on the production of respiration in hy¬ 
drogen offering an impediment to the passage of the blood; for the 
motion of the blood in the arteries, as Bichat and Emmert showed* 
continues in such cases for a certain time undisturbed. 
Dr. Goodwin attributed the depression of the circulatory powers, 
after interruption of {die respiration in the higher animals, to the cir¬ 
cumstance of the left ventricle ceasing to receive arterial blood, and 
supposed that the influence of this kind pf blood was indispensably 
necessary to the action of the left side of the heart. To this Bichat 
replied, that in animals of which the respiration is suspended, the 
dark blood coming from the lungs to the heart does not cause the 
immediate cessation of the contractions. This and other arguments 
adduced by Bichat* are not conclusive. It is not, however, at all 
probable that each side of the heart has a specific irritability for dif¬ 
ferent kinds of blood; for in the fœtus, in which the auricles commu¬ 
nicate by the foramen ovale, and in which there is no pulmonary 
respiration, but only some peculiar change effected in the blood in 
its passage through the placenta, both sides of the heart receive the 
same kind of blood. If the immediate action of bright red blood on 
the heart is really necessary to the maintenance of its action, Bichat’s 
explanation is much the more probable. He supposes that interrup¬ 
tion of the respiration deprives the heart of its irritability, by prevent¬ 
ing the supply of arterialised blood to the muscular fibres through the 
coronary arteries, which now carry dark venous blood. But although 
it appears certain that arterial blood does exert an influence on the 
heart’s action, yet the relative degree in which this influence and 
that of the nerves are necessary cannot be estimated; for all disturb¬ 
ances of the respiration produce corresponding disturbance in the 
action of the nervous system. 
2. Influence of the nerves on the heart’s action.—The influence 
of the passions, and other affections of the nervous system, on the 
heart’s action, is matter of constant observation. All sudden pas¬ 
sions at first disturb and then accelerate its action; the contractions 
becoming much more vigorous and frequent under the influence of the 
exciting passions, while they are rendered feeble, at the same time 
that they are accelerated by the depressing passions. 
Nevertheless, some persons have denied the dependence of the 
* Recherches sur la vie et la mort.


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