290 EXPEKIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES. 



one another by the use of different coloured inks. Fig. 135 repre- 

 sents graphically tlie tables of blood-pressure and pulse-rate in 

 Experiments I and II. We begin the pressure-curve by making 

 a dot on the first perpendicular, at a height corresponding to 

 the number 78. Passing along horizontally from this for a 

 space corresponding to 15 seconds to the abscissa, we make 

 another dot ; and at 10 seconds further, at a height correspond- 

 ing to 80, we make a third dot, and so on. We then connect 

 .the dots by lines, and tlms obtain the curves we wish. 



Fm. 135. 



Exp. 1. The straight line shows the biood-pressure, and the dotted line the 



pulse-rate. 



100 



Exp. 2. 



IV,— Determination of the exact Structures through 

 WHICH Drugs affect the Heart and Vessels. 



{British Medical Journal, 1871, December 9, p. 659, December 16, p. 687, 

 and December 30, p. 749.) 

 Comparison of the Effects of Drugs on different Animals in different Doses. — 

 Mode of determining the exact Cause of Symptoms. — Mode of raising Blocd- 

 pressure. — Modes of counting the Beats of the Heart. — Causes of Quickened 

 Pulse. — Direct Stimulation of the Sympathetic— Stimulation of Cardiac 

 G-anglia. — Paralysis of the Vagus-roots and Fibres, and of its Ends in the 

 Heart,— Causes of Slow Pulse. — Irritation of Vagus-roots. — Mode of sup- 

 plving the Head and Body with different kinds of Blood. — Indirect Irrita- 

 tion of Vagus-roots through the Blood-pressure : mode of lowering and 

 raising it. — Reflex Irritation of Vagus-roots. — Indirect Irritation through 

 the Respiration.- Irritation of Vagus-fibres. — Increased Conducting Power 

 of Fibres. — Stimulation of Vagus-ends. — Paralysis of the Sympathetic. — 



