1892.] Adductor' Fibres of the Recurrent Laryngeal Nerve. 107 



Division of Subject awd Analysis of Results. 



A. Division of Subject. 



The first part of the following research consists in the separation 

 and isolation of the different bundles of nerve fibres of which the 

 nerve trunk is composed, electrical excitation of each separate bundle, 

 and observation of the effects produced on the vocal cords by such 

 excitation. 



Exposure of the different bundles of nerve fibres under exactly 

 similar circumstances to the drying influence of the external air, with 

 observation of the relative duration of vitality possessed by the 

 different bundles, forms the second part of the investigation. 



Other methods were next instituted to control the results of the 

 foregoing, and the first of these, constituting the third part of this 

 work, consisted in tracing by post-mortem dissections each bundle of 

 nerve fibres separated in the nerve trunk to its termination in the 

 mucous membrane or in a muscle of the larynx. 



The next control method consisted in exposing the muscles of the 

 larynx immediately after death, and direct observation of them during 

 excitation of the separate bundles of nerve fibres, this being con- 

 trolled by occasional excitation of individual muscles themselves. 

 This forms the fourth part of the investigation. The fifth or last 

 part of the research served as a third control method, and consisted 

 in observations of the muscular degenerations which followed division 

 of one or other bundle of nerve fibres in the nerve trunk, three weeks 

 after such division. 



B. Analysis of Results. 



Section 1 . Separation and Excitation of the Individual Bundles of which 

 the Nerve is composed. — The separation was brought about by means 

 of an exceedingly delicate thin-bladed knife. The divisions between 

 the different bundles of fibres could usually be seen by the naked eye, 

 and further guides were the minute capillary twigs which usually 

 course on the surface of the nerve along these lines of division. 

 When no such guides could be seen by the unaided eye, a lens was 

 used to assist in their recognition. Grreat care was taken to preserve 

 the vitality of the nerve fibres by constantly bathing them with 

 warm normal saline solution. Each bundle was in turn raised into 

 the air, and stimulated by means of fine platinum electrodes attached 

 to the secondary coil of a du Bois-Reymond's inductorium, supplied 

 by a bichromate cell. The same strength of current was used for all 

 the bundles of nerve fibres in any given experiment, and was on an 

 average 5000 to 7000 on Kronecker's inductorium scale; and the rate 

 of interruption was 100 per second. The results in twelve dogs 



