38 SCIENCE PROGRESS. 



effective lumbar ramus or rami supplies a strip of skin im- 

 mediately below the sacrum. 



The second sacral supplies the hairs dorsal to the anus; 

 the third, those about one inch below the anus ; and the 

 coccygeal, the remainder to the tip of the tail. 



Now, by a comparison of the full areas supplied by the 

 anterior spinal roots with the areas of the grey rami, the 

 accurate connection of any anterior root with the ganglia, 

 or conversely of any ganglion with the anterior roots, can 

 be determined ; and Langley, in his later paper, gives a 

 series of tables^ in which this has been done. 



In a few experiments on the dog, Langley found that 

 the general arrangement of these fibres is the same as in 

 the cat. 



Where, as is usually the case in tracing the course of 

 these sympathetic fibres, we find that their path is made up 

 of two segments, each consisting of a nerve cell and its 

 fibre, the upper fibre whose cell is placed in the spinal cord 

 and which terminates in dendrites in one or other of the 

 ganglia of the system is termed by Langley the prse- 

 ganglionic fibre. The other fibre, whose cell is placed in 

 the ganglion and whose fibre runs, as a rule, to the nerve- 

 ending in the organ, he terms the post-ganglionic. 



In considerino^, moreover, the oriofin of the different 

 fibres in the lumbar region, there are other points of nomen- 

 clature adopted by Langley which are of great importance. 

 As the number of thoracic and lumbar nerves is very 

 variable, and as the first sacral is a nerve which is always 

 readily distinguished from all others, he starts with this as 

 his fixed nerve. The immediately preceding seven nerves 

 are called the first, second, etc., lumbar nerves successively.^ 

 If there is another lumbar nerve above that, it is termed 

 the extra lumbar. Sometimes, moreover, the seventh nerve 

 above the first sacral has a small rib, but this he still terms 

 the first lumbar nerve. 



Langley^ also describes the lumbo-sacral plexus of the 



^ Loc. at., pp. 220, ei seq. 



^ See Langley, y^'z^r;?. of Physiol. , vol. xvii., p. 297, 1894-5. 



^ Loc. cit., p. 296. 



