298 



PROFESSOR C. R. MARSHALL ON 



The slowing of the respiration produced by tutin during anaesthesia is not altered 

 by division of the vagi. In a rabbit anaesthetised with chloroform the injection of 

 0*0005 grm. tutin intravenously before division of the vagi reduced the number of 

 respirations from 115 to 60 per minute; after section of the vagi the same dose 

 caused the number of respirations to fall from 85 to 50 per minute. 



If the brain is excised and the administration of the anaesthetic afterwards stopped, 

 the injection of tutin produces an effect similar to that observed in an uninjured 

 animal. The action of a large dose up to the onset of convulsions is seen in the follow- 

 ing experiment : — 



Experiment VII. — Rabbit. Ether. Section through Posterior Part of Mid-brain. Brain above Level 

 of Section removed. Amesthetic stopped. Blood Pressure from Right Carotid Artery. Respirations 

 counted. 



1 



Time. 



Blood Pressure 



Pulse Rate per 10". 



Respirations 

 per 10". 





in mm. 



3.30 



65 



44 



9 



3.35 



0"01 grm. tutin injected 



into right facial vein. 





3.36 



71 



44 





3.37 



83 



38 



11 



3.38 



88 



34 



12-5 



3.40 



93 



36 



155 



3.42 



96 



36 



17 



3.43£ 



Clonic convulsions. 







The effect, particularly on the pulse rate, is much less than in a normal animal, but 

 this is probably due to the medullary centres being still influenced by the previous 

 administration of the anaesthetic. 



In a normal animal the dyspnoea produced by tutin is largely inspiratory in 

 character, and in the slow respiration occurring during anaesthesia it is the inspiration 

 which is mainly affected. It is not only increased in depth, but, when completed, is 

 also maintained for a relatively long period. The effect is shown in fig. 3, which also 

 illustrates the action of an allied substance, coriamyrtin, injected subsequently. The 

 latter tracing further illustrates the irregularity of the respiration which not 

 infrequently occurs after the administration of these substances. The respiration in 

 this experiment and in most others, owing to the late appearance of the effects, was 

 recorded by the diaphragm method described by Head ; but the same result was 

 obtained when a record of the respired air was taken by connecting the tracheal 

 cannula with a tambour. 



The slow breathing produced by moderate doses of tutin or coriamyrtin can 

 usually be abolished by pushing the anaesthetic, but if a large dose has been ad- 

 ministered deeper anaesthesia causes further slowing, which is quickly succeeded by 

 cessation of the respiration. If constant anaesthesia is maintained, the respiration after 

 a variable period generally assumes its previous frequency ; but a certain degree of 



