FUNCTIONS OF THE BRAIN 941 



muscles to a portion of a nerve coming off from an uninjured region 

 of the cord. 



By such operations it has been possible to transpose motor areas 

 on the cerebral cortex associated with the flexion arid extension 

 of a particular joint, so that the part of the cortex which originally 

 caused flexion after the nerve anastomosis causes extension, and 

 vice versa. When the nerves supplying a group of muscles of the 

 dog's fore-limb are eliminated, the nerves of the antagonistic group 

 may be used to supply both groups, and co-ordinated movements 

 may be restored, although this does not occur so rapidly as when 

 the nerves supplying the two groups are simply cut and cross- 

 sutured (Kennedy). However, the limitations of this method 

 ought to be recognized. Before any anastomosis of nerves can be 

 made, good fibres must first be destroyed. Under favourable cir- 

 cumstances these may all regenerate and find their way to the struc- 

 tures they are intended to innervate. When regeneration is com- 

 plete, the number of fibres capable of functioning will at best be the 

 same as before the operation, and may easily be considerably less. 

 The benefit, whatever it is, will be associated solely with the re- 

 distribution of the fibres. There is reason to think that the closer 

 to the cell of origin a nerve is injured or divided, the less is the chance 

 of restoration, and Feiss has found that after lesions in the cord 

 or the spinal roots neither the anatomical pattern of the affected 

 nerves nor their functional power is much affected by subsequent 

 nerve anastomosis. 



The central end of any efferent somatic fibre can also make 

 functional union with the peripheral end of any of the efferent fibres 

 which run from the central nervous system and end in ganglion 

 cells (pre-ganglionic fibres), and the central end of any pre-gan- 

 glionic fibre can do the same with the peripheral end of any efferent 

 somatic fibre (Langley and Anderson). For instance, Langley 

 divided (in cats) the vagus nerve and the cervical sympathetic. 

 The peripheral end of the former degenerated, of course, below the 

 section, and the peripheral (cephalic) end of the latter degenerated 

 above the section, up to the terminations of its axons in the 

 superior cervical ganglion. The central end of the cut vagus was 

 subsequently sutured to the peripheral end of the cut sympathetic. 

 After a time the vagus-fibres grew along the course of the degener- 

 ated sympathetic up to the ganglion, where some of them formed 

 arborizations around the ganglion cells. It was now found that 

 stimulation of the vagus produced the effects usually caused by 

 stimulation of the cervical sympathetic for example, dilatation 

 of the pupil and constriction of the bloodvessels of the head and 

 neck. From these experiments it follows that the functions of the 

 various groups of fibres in the cervical sympathetic do not depend 

 on anything peculiar to the fibres; any fibre which can make con- 



