234 A MANUAL OF PHYSIOLOGY 



tinues steadily to discharge itself along the efferent paths, whose 

 synapses are situated beyond the anaemic region. Section of 

 the bulb above the level of the respiratory centre, and of the cord 

 below the origin of the phrenic nerves, in addition to the anaemia, 

 makes no essential difference in the result. The initial rate of 

 discharge of the centre thus isolated from afferent impulses is 

 approximately constant in different experiments (about four a 

 minute in cats). 



Action of Drugs on the Respiratory Centre. The respira- 

 tory centre is directly affected by numerous drugs. Pituri and 

 nicotine, for instance, cause in various animals a quickening and 

 deepening of the respiration, followed, if the dose has been large, 

 by slowing and ultimate cessation. The action of the great 

 majority of such substances, however, possesses only a pharmaco- 

 logical interest, and it would be out of place even to enumerate 

 them in a text-book of physiology. But there are one or two 

 points in the action on the respiratory centre of chloroform and 

 alcohol substances so greatly employed in practical medicine 

 and in physiological research which may properly be touched on 

 here. 



Chloroform. The cause of the deaths from chloroform which, 

 at rare intervals, startle the operating theatre of every great 

 hospital where this anaesthetic is used, has been, on account of 

 its extreme practical interest, the subject of prolonged discussion 

 and experiment. Is it the heart that fails ? Or is it the respira- 

 tion ? The answer of what is known as the ' Edinburgh School ' 

 was that the respiration (in physiological terms, the respiratory 

 centre) is always first paralyzed. Their golden rule of doctrine 

 in chloroform administration was, ' Watch the respiration ; 

 the heart will take care of itself ' a rule which, however, in 

 ' Edinburgh ' practice did not exclude careful observation of 

 the pulse. This view, having the merit of simplicity, was 

 widely adopted. It was upheld by a scientific commission 

 appointed by the Nizam of Hyderabad to investigate the ques- 

 tion with the aid of modern physiological methods. But the 

 conclusions of the Hyderabad Commission seem to have been 

 too absolutely drawn. For it has been shown by a number of 

 observers that chloroform may paralyze the heart without 

 primarily affecting the respiration ; and, further, that paralysis 

 of the vaso-motor centre, and the consequent withdrawal of 

 blood from the heart and brain to the dilated splanchnic area, 

 may be an important factor in bringing about a fatal result 

 (p. 174). In normal chloroform anaesthesia in man it is easy to 

 demonstrate by the sphygmomanometer a fall of blood-pressure 

 in the brachial artery of 20 to 40 mm. of mercury (Hill). It would 

 seem that death from chloroform may take place either from 



