MOVEMENTS OF RESPIRATION ON THE CIRCULATION OF THE BLOOD. 593 
former may, however, be distinguished from the latter, first, by the length of the inter- 
val which elapses after the introduction of air before the effect manifests itself; and 
secondly, by the circumstance that it is not produced at all unless the animal has been 
for some time deprived of air, so as to weaken the action of the heart and diminish the 
arterial pressure by several inches. 
Finally, the relation between the respiratory movements, the arterial pressure, and 
the frequency of the contractions of the heart, in the dog, has been shown to be the 
opposite of that hitherto supposed to exist. Inasmuch as many of the conditions on 
which this relation depends are not the same in animals of different species, the relation 
itself is no doubt subject to corresponding modifications; but it maybe assumed that in 
all animals having hearts of the same structure, variations in the quantity of blood con- 
tained in the venae cavae influence the mode of contraction of the ventricles, and conse- 
quently the arterial tension, in the same way as in the dog. 
Note . — Professor Valentin, of Berne, in his recently published work (Versuch einer 
physiologischen Pathologie des Herzens, Leipzig, 1866) gives the results of observations 
made on Marmots during their winter sleep as to the relation between the respiratory 
movements and the arterial pressure. In the Marmot, when in profound sleep, the con- 
tractions of the heart occur at long intervals, which, however, are much exceeded in 
duration by those which separate the respirations. By connecting the carotid artery 
with the kymographion (which can be done without waking the animal), a tracing was 
obtained from which it appeared that the mercurial column sank during the first third 
of inspiration, rose during the second two thirds, continued to rise during the beginning 
of expiration, and again fell during the remainder. Of these facts he gives the following 
theoretical explanation : — “ The negative inspiration-pressure not only sucks air into the 
lungs, but blood towards the heart. The greater impletion of the heart enables it to 
propel more blood into the arteries, and increases its frequency, while its contraction as 
compared with its relaxation is prolonged. Expiration produces an opposite result ; for 
it facilitates the emptying of the lungs of blood, and adds to the systemic pressure. But 
inasmuch as the heart becomes less and less full during expiration, the increase of pressure 
is limited to the commencement of the expiratory act, a smaller quantity of blood being 
injected into the arteries. At the same time the duration of the contraction diminishes, 
while that of relaxation increases ” (p. 353). Here the author appears to attach much 
more importance to the direct influence of expiration than the facts warrant. 
Explanation of the Plates. 
In each figure the upper tracing is that produced by the lever connected with the 
Dynamometer, and expresses the variations of arterial pressure ; the lower by the lever 
connected with the caoutchouc bag, and expresses the movements of air in and out of 
the chest. 
In the arterial tracing three-tenths of an inch of vertical measurement correspond to 
