572 
BE. SANDEESON ON THE INFLUENCE EXEECISED BY THE 
greater or respiratory wave and the thoracic movements, it appeared to Ludwig that 
the descending limb (or to speak more shortly, the descent ) of the wave was coincident 
with the expansion of the chest in inspiration, and that the ascending limb (or ascent) 
corresponded to the time occupied by the. collapse of the chest in expiration and the 
succeeding pause, so that the summit of the wave indicated the commencement of inspi- 
ration. And with respect to the smaller or cardiac waves, he observed that in the ascent 
of the great wave they were more frequent and more abrupt than in the descent, whence 
he inferred that during expiration the contractions of the heart succeed each other 
with great rapidity and are separated by short periods of relaxation, whereas during 
inspiration the heart remains relaxed for some time between each contraction and its 
successor. 
In most of these experiments the arterial pressure only was traced on the cylinder of 
the kymographion ; as, however, it was found that under certain circumstances the rela- 
tions between the respiratory movements and the undulations of the tracing were obscure, 
the experiment was modified. An elastic bag containing air was introduced into the 
cavity of the pleura by an aperture to which the mouth of the bag fitted air-tight. The 
bag was connected by a flexible tube with a second bag, the expansive movements of 
which were transmitted by a lever to the cylinder of the kymographion, on which a 
tracing was inscribed simultaneously with that which indicated the arterial pressure. 
It was found that the expansion of the bag connected with the pleura did not always 
coincide with increased arterial pressure. These inconsistencies did not, however, 
appear to be of such a nature as to render it necessary to abandon the theory which 
had been adopted. Although Ludwig had evidently some misgivings as to its truth, 
he did not continue the investigation ; for in a prefatory note to a paper by Einbrodt, 
published in 1859, Ludwig states that during the preceding twelve years he had aban- 
doned the inquiry although convinced that he had misunderstood the connexion of the 
facts*. 
[Note . — In the last edition of his 4 Lehrbuch der Physiologie,’ Ludwig gives the fol- 
lowing account of the changes of arterial pressure consequent on the respiratory move- 
ments : — “ At the beginning of expiration the contractions of the heart become more 
frequent, the mean tension of the blood increases, so that even during the relaxation of 
the heart it sinks very inconsiderably or not at all. Every new contraction induces a 
higher tension than its predecessor. At the close of the expiratory movement, when 
the narrowed thorax resumes its normal size, a long pause in the heart’s action suddenly 
occurs, during which the tension sinks considerably, and the movements of the heart are 
in consequence retarded.” This passage shows that until 1861 the author entertained 
the same views as in 1859.] 
In 1860 Ludwig’s experiments were repeated by Einbrodt, who published his results 
* “ Ich Latte mich iiberzeugt dass ieh in meiner friiheren Arbeit die an nnd fiir sicL richtigen Thatsachen 
nicht ricbtig verkniipft Latte.” 
