OF THE CALABAR BEAN. 753 



26 minutes afterwards, cardiac contractions = 9 per min. 



98 o / Very feeble. Heart dark during 



" " I systole. 



30 „ „ = 7 „ 



35 „ „ irregular ; four ventricular for six auricular. 



Irregular and unrhythmical contractions continued for many hours afterwards. The final 

 stoppage was in diastole. 



It may now be useful to examine what connection exists, as cause and effect, 

 between the impairment and cessation of the respiratory movements and the 

 interference with, and stoppage of, the cardiac contractions, especially as so 

 deservedly distinguished a physiologist as Harley has asserted that Calabar bean 

 is a respiratory poison purely, which causes death by destroying the conductivit}' 

 of the motor nerves of respiration. Christison, in his investigation, was the first 

 to observe an action on the heart, and he believes that death is caused by para- 

 lysis of that organ. My former results were, so far, in accordance with this state- 

 ment ; but they also show that death may often be due to asphyxia, and while I 

 agree with Harley in this, I believe him to be in error when he asserts that 

 paralysis of the motor nerves is the cause of such death. The data that have 

 already been given are sufficient to prove that motor nerve conductivity is always 

 retained, in warm-blooded animals as well as in cold, for many minutes after the 

 complete stoppage of respiratory movements, and that such stoppage is due to 

 destruction of the reflex and co-ordinating functions of the medulla spinalis and 

 oblongata. To complete this evidence, it will be sufficient to show that no con- 

 nection of cause and effect necessarily exists between the impaired respiratory 

 movements and the cardiac paralysis. 



Experiment LVI. 



In a large retriever dog, it was found that the mean number of respirations was ten, and 

 the mean number of cardiac contractions 126, during seven minutes immediately preceding the 

 injection of six grains of extract, suspended in water, into the right jugular vein. 



1 min. after the injection, the respirations = 10, cardiac contractions = 78 per min. 



— 11 =54 



— 9 = 40 



— 9 =8 

 = 10, „ =20 „ 

 = 10, „ = 16 



— 9 =9 

 » >> — o, ,, y> ,, 



This experiment gives the result that, in one minute and thirty seconds after 

 the poison was administered, the number of cardiac contractions had fallen to less 

 than one- half, while the respiratory movements had increased by one per minute; 

 and it distinctly shows the absence of any respiratory change to cause the marked 

 effects that were produced on the heart's action. 



1 „ 30 sec. 



9 



2 



3 , 



\ o " 



7 , 



, o „ 



9 , 



, o „ 



10 , 



, o „ 



10 . 



, 30 „ 



