286 MESSRS. F. GOTCH AND V. HOESLEY 



5. Preparation of the Spinal Cord for Excitation. 



Another mode of preparation remains to be referred to, that, namely, in which the 

 cord, when severed from its connection with the brain in order to investigate the 

 functions of the lower fragment, is to be excited. 



It was necessary for these experiments to sever the cord as high as possible, 

 though, as a matter of fact, it was found advisable not to perform the operation at a 

 higher level than that of the 7th dorsal vertebra, otherwise, serious impairment 

 of respiratory and vase-motor functions followed, and profound shock vitiated the 

 experimental results. When the upper end of the lower fragment of cord was to be 

 excited, this was further exposed, and a piece 5 mm. in length excised on the peri- 

 pheral side of the section, so that by looking into the gap the structures on the cut 

 surface of the cord could be seen and the excitation localised. The gap was made 

 absolutely dry with amadou and small pieces of sponge when the cord was to be 

 excited. 



Finally, a series of experiments involved the division of the cord at two levels. A 

 portion was thus cut off, both from the brain and from the lumbar plexus, and prepared 

 so that one end could be connected with the non-polarisable electrodes and observed 

 whilst the other was excited. In all these cases the upper division was effected first, 

 so as to diminish the shock which the further operative procedure connected with the 

 lower division caused. The end with which it was desired to connect the electrodes 

 was then carefully exposed, ligatured and freed from its connections, as already 

 described under (3), whilst the other end was prepared for excitation. 



6. Preparation of the Roots of the Nerves. 



The posterior and anterior roots were in some instances prepared for excitation, in 

 others for observation. In both cases the roots chosen were those forming- the cauda 

 equina, and they were exposed by a suitable opening of the spinal canal and theca in 

 the manner previously indicated. The roots were carefully separated and when 

 required each one was ligatured near its peripheral attachment and divided. Great 

 care is necessary to avoid pulling, drying, &c., in the case of the roots. (See 

 Plates 34 and 35.) 



7. Section of Columns of the Cord. 



In many experiments it was necessary to make a section of one or more of the 

 columns of the cord between the part excited and the part observed. The method 

 employed was to expose a portion of cord for the purpose and then to make the 

 section by means of BEER'S cataract knife, completing it by means of a fine-cutting 

 needle or occasionally fine-pointed sharp scissors. In every case the limitation of the 

 section was ascertained by post mortem examination. When a hemisection of the cord 



