1893.] of the Sympathetic Nervous System. 551 



other dividing lines between the areas vary not inconsiderably in 

 position. 



The 2nd sacral ranrns, as a rule, supplies the hairs of the tail just 

 above the level of the anus and over it ; the 3rd sacral ramus supplies 

 the hairs for about an inch and a half below the level of the anus. 

 The coccygeal ganglion gives off rami to the several coccygeal nerves, 

 and these supply different lengths of the tail. This ganglion supplies 

 by its rami the whole, or nearly the whole, of the tail. 



The distribution of the pilo- motor post-ganglionic fibres of each 

 spinal nerve, i.e., of the fibres which run to each spinal nerve from 

 the sympathetic system, can also be determined by stimulating the 

 nerve inside the spinal canal. This method depends upon the 

 spreading of the current down the nerve to its dorsal branch, in 

 which the pilo-motor fibres run. In most cases rather strong shocks 

 are required ; in others, as in the sacral region, moderate shocks are 

 sufficient. A similar spreading down of the current to the ventral 

 branches of the nerves may perhaps be the explanation of the 

 assertion that the lower lumbar nerves contain direct spinal secretory 

 and vaso-motor fibres for the foot. When a spinal nerve sends pilo- 

 motor fibres (pre-ganglionic fibres) to the sympathetic, as well as 

 receiving some from it (post-ganglionic fibres), the two can readily 

 be distinguished by injecting nicotine. This cuts out the effect of 

 the pre-ganglionic, but not that of the post-ganglionic, fibres. 



So far, I have been chiefly concerned with the description of the 

 portion of the dorsal skin innervated by each ganglion through its 

 grey ramus. The next question to consider is the connexion of each 

 ganglion with the spinal cord. Like the other questions dealt with 

 here, this must be treated somewhat broadly, since there are more 

 or less pronounced individual variations. 



In the following table I give what appear to be the ordinary con- 

 nexions* in an animal in which the 4th lumbar nerve and the 6th 

 lumbar sympathetic grey ramus contain no pilo-motor fibres. I omit 

 the connexion of the 4th and 5th spinal nerves with the sympathetic 

 ganglia. I insert the connexions of some spinal nerves which do 

 not contain pilo-motor fibres. In the left-hand vertical column, the 

 numbers refer to the spinal nerves arranged in order, beginning with 

 the 1st thoracic. The numbers placed in a horizontal line with the 

 number of each spinal nerve represent the sympathetic ganglia in 

 which its fibres make connexion with nerve-cells to issue in the 

 corresponding grey rami. S.c.,g. and g.st. are used respectively 

 for the superior cervical ganglion and the ganglion stellatum. When 

 either of these, or the number of a ganglion, is enclosed in brackets, 



* The connexion of the nerves with the uppermost and lowermost of their series 

 of ganglia is sometimes slight only ; this is especially the case as regards the 

 connexion of the lumbar nerves with the uppermost of their series of ganglia. 



