COMPARISON OF EFFECTS OF DRUGS. 291 



Paralysis of the Cardiac Ganglia.— Part of the Ganglionic Apparatus 

 affected.— Nervous System in the Heart. — Motor Ganglia.— Stimulating 

 Ganglia. — Inhibitory Ganglia. — Connecting Apparatus. — Action of Drugs 

 on the Inhibitory Apparatus. — Nicotia, Muscaria. — Antagonism of Atropia 

 and Physostigma ; bearing of this on Therapeutics. — Paralysis of Co-ordina- 

 ting Apparatus. — Paralysis of the Muscular Fibres of the Heart. — Blood- 

 pressure : mode of determining whether Changes in it are due to Alterations 

 in the Heart or Vessels. — Elimination of the Action of the Heart : Division 

 of its Nerves. — Irritation of Vagus. — Ligature of Aorta. — Artificial Circu- 

 lation ; in Mammals, in the Frog. — Observation of Vessels. — Action on 

 Vaso-motor Centre ; on Vascular Walls. — Influence of the Action of Parts 

 surrounding the Vessels upon them. — Action of the Pulmonary Circulation 

 on the Blood-pressure. — Use of the Sphygmograph. 



Comparison of the Effects of Drugs. — Before proceeding to 

 examine separately the different structures through which a 

 drug may act on the blood-pressure, it is advisable to compare 

 the effects which it produces on animals of different kinds, such 

 as dogs and rabbits, as well as the action of larger and smaller 

 doses on animals of the same kind. Continuing to take as an 

 example the action of atropia, admirably investigated by Von 

 Bezold, we find the following results. 



With a small dose of atropia injected into the jugular vein 

 towards the heart : 



The blood-pressure rises in both rabbits and dogs : 

 The pulse becomes quick, rising in rabbits from 256 to 

 288 ; in dogs, from 80 to 240. 

 With a larger dose : 



The blood-pressure, in both rabbits and dogs, falls at first 



and afterwards rises to the normal. 

 The pulse becomes quick in both. 

 With an additional dose : 



The blood-pressure in rabbits falls very low as the poison 

 reaches the heart ; afterwards rises ; and falls again 

 below the normal. 

 The pulse becomes slower, and then quicker. 

 With a very large dose : 



The blood-pressure sinks instantly in both rabbits and 



dogs. 

 The pulse in rabbits becomes slower and weaker, and 

 then stops ; in dogs it becomes quick. 



u 2 



