238 Mr. R. Dunstan and Miss L. E. Boole. [June 20, 



existed a focus, excitation of which resulted in adduction of the vocal 

 cords, and another near to this, stimulation of which resulted in 

 abduction of the cords. While in the cat it was possible to differ- 

 entiate these movements without any preliminary measures being 

 adopted, it was otherwise in the dog, for it was only after the 

 adductor fibres of one recurrent laryngeal nerve had been divided 

 transversely that it first became possible to evoke abduction of the 

 vocal cords on excitation of the cortex, though in subsequent experi- 

 ments it was sometimes possible to evoke this movement on excita- 

 tion of the cortex of the dog without adopting this preliminary 

 measure. The other effect on the cords, which it was as a rule found 

 most difficult to differentiate from that of abduction, was acceleration 

 of their movements. 



In furtner exploring the cortex it was found that on the anterior 

 composite gyrus, below the abductor centre, there existed a focus, 

 excitation of which resulted in what is described as a clonic adductor 

 effect on the cords, in which the cords were first brought into a posi- 

 tion of moderate adduction, and then there was added rapid short to- 

 and-fro excursions. 



On passing within the confines of Spencer's area for arrest of 

 respiration, it was found that in the peripheral parts of this area 

 there existed three foci, excitation of which affected the cords in 

 different ways. The most anterior of these foci was responsible for 

 arrest of the cords in adduction, i.e., in the expiratory stage of their 

 excursions ; excitation of the focus behind this, and corresponding, 

 probably, to Horsley and Semon's abductor centre in the cat, was 

 followed by arrest of the cords in abduction, i.e., their inspiratory 

 position ; while the most posterior focus, which is situated at about 

 the junction of the anterior composite and anterior sylvian convolu- 

 tions, resulted in intensification combined with acceleration of the 

 movements of the cords when stimulated. Excitation of Spencer's 

 chief focus for arrest of respiration on the olfactory lobe, resulted in 

 arrest of the cords in the position they occupy during expiration in 

 dogs, and in the position they occupy during inspiration in cats. 



VI. " An Enquiry into the Nature of the Vesicating Constituent 

 of Croton Oil." By WYNDHAM R. DUNSTAN, M.A., F.R.S., 

 and Miss L. E. BOOLE, F.I.C., Lecturer on Chemistry in the 

 London School of Medicine for Women. Received June 5, 



1895. 



(Abstract.) 



The vesicating constituent, or more strictly, the pustule-producing 

 constituent of croton oil, has been the subject of investigation by 



