RELATION OF RESPIRATION TO THE NERVOUS SYSTEM 281 



generally accepted view, to be associated with spasm of the bronchial 

 muscles. 



Special Modifications of the Respiratory Movements. Cheyne- 

 Stokes Respiration is the name given to a peculiar type of breathing, 

 marked by pauses of many seconds alternating with groups of 

 respirations. In each group the movements gradually increase to 

 a maximum amplitude, and then become gradually shallower againf 

 till they cease for the next pause. The phenomenon often occurs in 

 certain diseases of the brain and of the circulation, and pressure on 

 the spinal bulb may produce it. In cats in which the circulation 

 in the -brain and medulla oblongata has been interrupted for a time 

 and then restored it is often noticed at a certain stage of resuscita- 

 tion of the respiratory centre. In frogs, Cheyne-Stokes breathing 

 has been observed as the result of interference with the circulation 

 in the spinal bulb, ' drowning,' or ligature of the aorta, and also as 

 a consequence of removal of the brain, or parts of it (hemispheres 

 and optic thalami) . But it is not peculiar to pathological conditions, 

 being also seen, more or less perfectly, in normal sleep, especially in 

 children, in healthy men at high altitudes, in hibernating animals, 

 and in morphine and chloral poisoning. 



Well-marked Cheyne-Stokes breathing can be obtained experi- 

 mentally in normal persons in a variety of ways. If, for example, 

 the subject is caused to breathe deeply and frequently for about two 

 minutes, so as to produce a prolonged apncea, the respiration, when 

 it is resumed spontaneously, is of the Cheyne-Stokes type (Haldane). 

 The explanation given by Haldane is that the fall in the partial 

 pressure of the oxygen in the pulmonary alveoli (p. 277) during the 

 primary apncea, with the consequent fall of oxygen pressure in the 

 arterial blood and the respiratory centre, leads to the production 

 of lactic acid in the respiratory centre and elsewhere, which stimu- 

 lates the centre in the same way as carbon dioxide, and thus permits 

 it to be excited by a smaller partial pressure of carbon dioxide than 

 that normally necessary. As soon as the pressure of carbon dioxide, 

 which is increasing during the period of apncea, has reached the 

 exciting value breathing is resumed. The respirations, beginning 

 as very feeble movements, rapidly increase in strength till the 

 breathing becomes quite deep or actually dyspnoeic. The store of 

 oxygen is replenished by this thorough ventilation of the lungs, the 

 changes in the excitability of the respiratory centre due to lack of 

 oxygen disappear (perhaps by oxidation of the lactic acid), and the 

 centre relapses into a period of repose. During this period of apnoea 

 the oxygen pressure sinks once more to the point at which the change 

 in the excitability of the respiratory centre by carbon dioxide occurs, 

 and the breathing again starts. In pathological cases the want of 

 oxygen may be associated either with deficient circulation through 

 the bulb-centre or with deficient intake by the lungs. The adminis- 



