36 SCIENCE PROGRESS. 



ramus, almost without exception, produced no effect, though 

 stimulation of the grey ramus produced the usual erection 

 of hairs over its especial area of supply. Each pilo-motor 

 fibre, therefore, leaves the cord in an anterior root and 

 passes by the white ramus communicans of that nerve to 

 the sympathetic system, and after a longer or shorter course 

 ends in connection with a cell or cells in a sympathetic 

 ganglion of the lateral chain. From this the impulses are 

 carried by a fibre or fibres to the grey rami, and thence to 

 their skin distribution. The ultimate distribution of the 

 fibres in a white ramus usually does not in any way 

 correspond to the distribution of the grey ramus running 

 from that ganglion. Thus, for example, stimulation of the 

 anterior roots of the eleventh thoracic nerves after previous 

 ligature and section produced erection of a longish strip of 

 hairs in the lumbar region, whilst stimulation of the grey 

 ramus of that nerve produced energetic erection of hairs in 

 a short strip a little distance above the long strip, and 

 separated from it by a quiescent region. The areas sup- 

 plied by successive anterior roots are found to form successive 

 strips which, however, frequently overlap one another to 

 a considerable extent. Langley ^ found that stimulation 

 of an anterior root with weak shocks produced an erection 

 of hairs supplied by all the fibres issuing by that root. Then 

 if the strength of the stimuli be considerably increased in 

 addition to the first effect, an erection of hairs in a narrow 

 strip supplied by the grey ramus running to that nerve is 

 now produced. The first effect is obliterated on paralysing 

 the ganglion cells by injection of nicotine whilst the latter 

 effect is of course unaffected. 



In the monkey, Sherrington showed that the pilo- 

 motor fibres found in the cervical sympathetic left the cord 

 by the second to the sixth thoracic nerves, and had gang- 

 lion cells upon their course in the superior cervical ganglion. 

 Thence they are distributed to the hair on the forehead, 

 front of scalp, temple, cheek and the upper part of the 

 whisker. 



^ Loc. cit., p. 203. 



