s. Simpson, Secondary Degeneration following Unilateral Lesions etc. 305 



for these nuclei" (cranial motor nuclei) "leave the main bundles" (of 

 the pyramidal tract) "and the exact path which they follow to the 



nuclei have not as yet been fully determined." "The statement 



that nerve fibres from these bundles do pass to these nuclei is based 

 mainly, but not solely, upon clinical experience, physiological experi- 

 ment, and analogy." That is to say, the anatomical connections of the 

 fibres of the pyramidal tract with the cells of the anterior cornua of 

 the spinal cord and of the cranial motor nuclei have never yet been 

 satisfactorily established, and it was with the object of throwing some 

 light, if possible, on this subject that the work embodied in the pre- 

 sent paper was undertaken. 



Method of Research. 



In that part of the research the results of which are contained 

 in this communication, sixteen cats and two monkeys were experi- 

 mented upon, and in all these an attempt was made to divide the 

 projection fibres arising from the left motor cortex in its whole ex- 

 tent. In other cases, in animals of the same species, partial cortical 

 motor lesions were made, but all the material has not yet been 

 examined, and of these the results will be given later when the whole 

 research is completed. In one case Professor Schäfer was good enough 

 to place at my disposal the brain and spinal cord of a dog in which, 

 in the course of another investigation, he had made a lesion in the 

 left motor cortex so that I might have an opportunity of examining 

 the secondary degeneration resulting therefrom. 



Operative Procedure. In each case the animal was fully an- 

 aesthetised with ether before the operation was begun, and was kept 

 under the influence of the anaesthetic until it was completed and the 

 wound closed and dressed. The hair was cut short and then shaved 

 off the left side of the skull. A skin flap was reflected and a small 

 trephine opening made through the bone as nearly as possible over 

 the area of the brain which it was desired to expose; this opening 

 was then enlarged with bone forceps, and the dura reflected so as to 

 expose the surface of the brain. 



In each of the sixteen cats used the lesion was practically the 



Internationale Monatsschrift für Anat. u. Pliys. XTX. 20 



