488 Mr. A. F. Dixon. On the Development of the [Mar. 21, 



upward path must be via grey matter, and probably subsequently by 

 one of the cerebellar tracts to the cerebellum. 



In the cases of section of the brachial and upper thoracic posterior 

 roots no degenerated fibres go into Goll's column, nor into Goll's 

 nucleus, but there is very extensive degeneration of Burdach's nucleus. 

 The upward path from the arm resembles therefore that of the leg in 

 respect to its upward projection toward the cortex. 



One of the chief results to which, in conclusion, we wish to draw 

 attention is the following : That afferent impulses, both from the 

 skin and from the muscles, especially the former, as related to the 

 palm and sole, are necessary for the carrying out of " highest level " 

 movements. 



It may be argued against this assertion that in animals it is impos- 

 sible'to obtain definite information as to whether the animal can not 

 or will not perform the movements the absence of which has been 

 described. 



From observations on tame animals we are, however, ourselves 

 firmly convinced that there exists actual inability to perform the 

 movements in question. The reasons for this belief wil 1 be detailed 

 in our fuller paper. 



IX. On the Development of the Branches of the Fifth Cranial 

 Nerve in Man." By A. FRANCIS DIXON, B.A., M.B., Chief 

 Demonstrator of Anatomy, Trinity College, Dublin. Com- 

 municated by Professor D. J. CUNNINGHAM, F.R.S. Received 

 February 22, 1895. 



(Abstract.) 



The investigation, the general results of which are summarised 

 below, was suggested to the author by Professor His, and part of the 

 work was carried on in his laboratory in Leipzig in the summer of 

 1893. Models were constructed of the cranial nerves in embryos of 

 different ages, and the branches present noted and measured. These 

 models were made up of glass plates, covered with varnish, on which 

 were drawn the outlines of the sections and the positions of the nerves, 

 &c. Detailed descriptions of the fifth nerve branches are given for 

 five different stages of the human embryo, beginning with an embryo 

 of four weeks, at which time merely the three main divisions of the 

 nerve are represented, and ending with one of the eighth week. 

 The observations on the human embryo have been checked by further 

 observations on rat embryos, and an almost complete correspondence 

 between the two has been made out. 



