550 Mr. J. N. Langiey. On the Arrangement [Feb. 9, 



The distribution of all these rami down to the 4th lumbar we may 

 consider together. 



The area of the 2nd thoracic ranms (or of the 1st, as mentioned 

 above) follows on the area of the lowest effective cervical ramus. 

 The 4th lumbar rarnus supplies either the skin over the 7th lumbar 

 vertebra and a small piece of sacrum, or the skin over the sacrum. 

 Between the limits just given for the 2nd thoracic and the 4th 

 lumbar the areas follow on each other, the length of each area 

 being about that of a vertebra. There are variations in the relative 

 length of the areas in different animals, but, generally speaking, we 

 may saj that in the thoracic region the areas are a little larger than the 

 neighbouring vertebrae, and in the upper lumbar region a little shorter. 



Below the 4th lumbar nerve we reach the hind leg region, which is 

 like that of the fore leg already mentioned, in so far as one, two, or 

 three nerves have no dorsal cutaneous branches to the mid-line, 

 and the corresponding rami have no pilo-motor fibres. These 

 nerves are the 5th, 6th, and 7th lumbar. On the rami of these 

 nerves I have made many more experiments than on the rami of the 

 ganglion stellatum, and, no doubt in consequence, I have found 

 greater variation. Thus, as I have said, I have not so far observed 

 any case in which the ramus to the 8th cervical nerve contained 

 pilo-motor fibres. In the lumbar region the 6th nerve is that which 

 most frequently has no pilo-motor fibres, but in two cases it appa- 

 rently did contain some; it is worth mention that in these cases 

 the lumbo-sacral plexus was an extreme form of my Class I* (posterior 

 type of arrangement, part of Sherrington'sf post-fixed plexus), the 

 7th nerve sending a filament to the obturator. The 5th lumbar ramus. 

 has pilo-motor fibres more commonly than the 7th. 



About the end of the sacrum appears to be the dividing line between 

 the areas of the rami which come from above and those which come 

 from below the ineffective ramus or rami. Thus the skin over the 

 lower part of the sacrum may be supplied by the 4th, 5th, or, perhaps, 

 the 6th lumbar ramus, the skin over the upper coccygeal vertebras by 

 the 7th lumbar or 1st sacral. In each case there are one or more nerves, 

 lying between the nerve which supplies the lower part of the sacral 

 region and that which supplies the upper coccygeal region, which con- 

 tain no pilo-motor fibres. This dividing line in the experiments in which 

 L have specially noted the point has only varied from a position mid- 

 way between the spine of the 2nd and 3rd sacral vertebras to a 



ntion a little below the spine of the 3rd sacral vertebra. As I 



have indicated earlier, the corresponding line in the upper thoracic 



i also appears to undergo very slight variations.: All the 



* ' Journ. of Physiol.,' vol. 12, p. 350, 1891. 

 f Ibid., vol. 13, p. 635, 1892. 

 t Cf. also p. 555, figs. 1 and 2. 





