1867.] Dr. J. Burdon Sanderson — Croonian Lecture, 391 



" On the Influence exerted by the Movements of Respiration on 

 the Circulation of the Blood." Being the Croonian Lecture 

 for 1867^ delivered by Dr. J. Burdon Sanderson. 

 (Abstract). 



The purpose of the lecture was to show that the explanation usually given 

 by physiologists of the mode in which the respiratory movements of the 

 thorax influence the force and frequency of the contractions of the heart 

 can no longer be entertained. 



The doctrine usually taught in this and other countries is stated as fol- 

 lows in one of the most recent text-books : — " During the act of expiration 

 the frequency of the pulse is considerably augmented, whilst the line of 

 mean pressure rapidly rises, indicating increased tension in the arterial 



walls During the act of inspiration, on the contrary, the pulsation 



becomes slower, the curves much bolder, and the line of mean pressure 

 gradually falls ; for then the blood readily enters the thorax, and, as a con- 

 sequence, the great veins, capillaries, and arterial walls become compara- 

 tively flaccid" (Carpenter's * Physiology,' 1864, p. 345). Statements to 

 the same effect are to be found in Budge's 'Lehrbuch der Physiologic,' 

 1862, p. 350; in Kirke's ^Handbook of Physiology,' 1863, p. 129; in 

 Ludwig's 'Lehrbuch,' 1857, vol. ii. pp. 161, 162. 



From numerous experiments, in which the respiratory movements and 

 the variation of pressure in the arteries in the dog were recorded simulta- 

 neously by mechanical means, the author had arrived at an opposite con- 

 clusion, viz. that in natural breathing each expansion of the chest is fol- 

 lowed by increase of arterial tension and shortening of the diastolic inter- 

 val ; in other words, that the immediate efi^ect of inspiration is to increase 

 both the force and frequency of the contractions of the heart. 



The experimental metJiod was as follows For the purpose of recording 

 the movement of air in and out of the chest, the animal is caused to breathe 

 through a T-shaped tube, one arm of which is connected with the trachea, 

 while the other remains open. By the stem it communicates with a disk- 

 shaped bag of thin caoutchouc. The resistance afi'orded to the ingress and 

 egress of air by the tube, although very inconsiderable, is yet sufiicient to 

 produce alternate movements of expansion and collapse of the bag. The 

 variations of arterial pressure are measured by a mercurial manometer, 

 diff'ering from that of Poiseuille, in that the attached arm, which is the 

 longer of the two, is of much smaller diameter than the other, the area of 

 the latter being twelve times as great as that of the former. For the pur- 

 pose of recording the movements of the dynamometer and of the caout- 

 chouc bag, two light wooden levers of the third kind, each 25 inches in 

 length, are used. These work on steel axes, the bearings of which are so 

 contrived that the axis of the arterial lever is directly above that of the 

 respiratory lever, and that both oscillate in the same vertical plane : bi 

 vertical rods they are connected, the upper or arterial lever vdth a cork float 



2 K 2 



