582 
DR. SANDERSON ON THE INFLUENCE EXERCISED BY THE 
1 (fig. 1). Cork B was inserted in the tube, but by inadvertence a second aperture in 
the caoutchouc bag intended for a different purpose was left open. As it was of equal 
diameter with the tube by which the bag is connected with the trachea, the resistance 
offered by the apparatus in this instance was extremely small. This is indicated by the 
inconsiderable extent of the oscillations of the respiratory lever. Measurements show 
that the acceleration of the contractions of the heart, and the increase of arterial pres- 
sure, occurred invariably two-thirds of a second after the commencement of each inspi- 
ration. 
2 (not engraved). Cork B was again used, but the second opening in the caoutchouc bag 
was closed. The increased resistance is denoted by the depth of the inspiratory descent. 
The characters of the arterial tracing remain unaltered. It is to be observed that when- 
ever inspiration was performed with greater suddenness than usual, its influence on the 
arterial tracing was more transitory, and the interval between the inspiratory act and 
its effect was shorter. 
3 (fig. 2). Cork C was employed. The extent of movement of the lever was much 
increased, but the characters of the arterial tracing are the same. 
4 (fig. 3). By inserting the cork D, which almost filled the aperture of the ~y tube, 
the resistance was increased to the utmost. The main features of the arterial tracing 
are unchanged, but the variations of arterial pressure occur at a shorter interval, viz. 
four-tenths of a second after the thoracic movements. The breathing was slightly acce- 
lerated, the number of respirations per minute being thirteen as compared with eleven 
at the beginning of the period of observation. 
5 (not engraved). The cork A was substituted for D. The breathing appeared to be 
perfectly free, the extent of movement of the lever being scarcely greater than when 
the aperture was left entirely open. 
6 (not engraved). Soon after the last observation, viz. an hour and five minutes after 
the commencement of the experiment, the breathing became irregular, the respiratory 
movements becoming unequal both in duration and depth, although no change was 
made in the apparatus. The effects of these variations are seen in the tracing. 
7 (fig. 4). In order to carry the investigation one step further the open arm of the 
T tube was completely closed, so that the limited quantity of air contained in the con- 
necting tube and in the caoutchouc bag was repeatedly respired. The tracing was made 
during a period commencing twenty- three seconds after this had been done, and shows 
that the movements of the respiratory lever were still more ample, and particularly that 
the inspiratory efforts were so energetic that the caoutchouc bag was emptied each time 
the chest expanded. This is indicated by the horizontal line between the descending 
and ascending limb of the curve. The breathing was scarcely at all accelerated (12-14 
per minute), and the arterial tracing retains the same character as before. The increased 
arterial tension and acceleration of the pulse lasted in each case during the whole of the 
period of inspiration. 
The series of results just stated afford evidence that the relation previously observed 
