430 Bayliss and Starling, 



Method of Experiment. Large dogs only were used; tliese were 

 anaesthetized with a hypodermic injection of morpliia, half to one horn- 

 before the experiment, and during the latter by the inhalation of a 

 small amount of A. C. E. mixture, in addition. The left carotid artery 

 was dissected out in the neck, and the heart catheter, consisting of a 

 piece of German silver catheter tube open at the cardiac end and 

 provided with a stopcock at the other end, which fitted tightly the 

 nozzle of the lead tube of the manometer, was inserted into the 

 central end, and gently pushed down between the semilunar valves 

 into the left ventricle. After a few trials, it is easy to do this, and 

 the sudden change of the beats of the upper end of the tube indicates 

 when the cavity of the ventricle is reached. There is thus an open 

 communication between the manometer and the heart cavity. Clotting 

 very rarely occurs when the catheter has been previously completely 

 filled by 25 % Magnesium sulphate solution, no doubt because such a 

 very minute quantity of blood enters the tube at each beat. The 

 vagi were usually cut and the peripheral end of one of them prepared 

 for excitation. 



The Intraventricular Pressure Curve. 



The general form of the curve is as described originally by 

 Chauveau and Marey ^) and confirmed by Fick^), Frédéricq^), and 

 Hürthle^), and consists of: 



1. A very steep ascending limb; 



2. A plateau nearly parallel to the abscissa, or ascending or 

 descending, and having upon it three waves more or less sj' 

 wellmarked; and 



3. A very steep descending limb. (Figs. 2, 3, 4, 5, and 6. 

 Plate XX.) 



The auricular beat is generally shown by a slight elevation at 

 the foot of the ascending limb, (seen best in Figs. 4 and 5, under 



^) Gazette méd. de Paris. 1861, p. 320. 



-) Pflüger's Archiv. XXX, p. 600. 



^) Travaux du laboratoire. II, pp 73, 74. 



*) Pflüger's Archiv. XLIX, pp. 29 et seq. 1891. 



