EXAMINATION OF SOME SPINAL NERVES 123 
The fibres in the motor roots of tlie brachial region are, as I have pointed out also for 
those of the lumbo-sacral region, from their very origin commingled in such a way that any one 
root-filament contains motor fibres for a variety of mviscles, and often for muscles not concerned 
with the same simple movement of the limb. Commingled in this way at their source, they, 
after entering the nerves of the plexus, become sorted out into proper groups destined for 
particular muscles ; hence the possibility of carrying out such dissections as those of 
Herringham* in spite of the difficulties on which W. KRAUSEt has so much insisted, and 
indeed stated to be insuperable. But within the motor roots themselves tlie fibres are so com- 
mingled that it is impossible, in one and the same root, to obtain, for instance, a bundle of fibres 
in one part of the root which represents flexion of the wrist, and a bundle in another part of the 
root which represents extension of the wrist. 
It is clear that examination of the fore-limb does not, any more than did that of the hind- 
limb,t support W. Krause's§ statement that the skin at the free end of the limb is innervated by 
the nerve-fibres which, among fibres for the limb, are the ones most segmentally posterior ; that 
opinion is clearly no longer tenable. Krause, from his experiments and dissections on Lepm and 
Cynomolgus, also supported the 'law' of Vanderkolk|| and Hilton,1I to wit, that a muscle is 
supplied with nerve-fibres by the same spinal nerve as innervates the skin overlying it. In this 
again Krause is as directly controverted by examination of the fore-limb as of the hind. Also, 
in speaking of the longest nerve-fibres, as those in the Vlllth cervical root, Krause must be 
ignorant of the fact that the 1st and Ilnd thoracic roots send nerve fibres to the intrinsic muscles 
of the hand. 
SECTION IV.— SPINAL REFLEX ACTION 
The above examination of the peripheral distribution of the roots of the spinal nerves was 
undertaken as a 'step preliminary to observations on the reflex functions of tlie spinal cord.'** 
Methods employed. 
For the purpose in view I found it essential to transect the cord; for the hind-limb region 
this was done sometimes at low levels, more usually above the 1st cervical root; almost 
exclusively at the latter situation in all experiments on the fore-limb region. In some experi- 
ments, as a control upon the spinal, transection was made at prepontine levels. It might have 
been thought that to examine spinal reflexes {e.g-, those confined to spinal paths) chemical narcosis 
would have sufficed, the longer and encephalic paths being blocked earlier than the spinal. But 
as the experiments of Marshall HALL,tt Bernstein, and Cayrade§,§ showed, the reflex 
* 'Proceedings of the Royal Society,' vol. ^i, p. 440, 1887. 
t ' Beitriige zur Anatomic der oberen Extreniitat.' Leipzig 
u. Heidelberg, 1863. 
X 'Phil, Trans.,' B, vol. 184, p. 641. 
§ ' Beitrage zur Anatomie der oberen Extremitat.' Leipzig 
u. Heidelberg, 1863. 
II Froriep's 'Notizen,' 3rd series, 4, izg, 1847. 
^ 'Rest and Pain.' London, 1857. 
** 'Phil. Trans.,' B, vol. 184, 1893. (Section IV of this 
paper formed the matter of the Croon ian Lecture 
before the Society, April, 1897.) 
ft 'Synopsis of the Diastaltic Nervous System.' London, 
1850. 
Schmidt's ' Jahrbiicher,' vol. 142, p. 227, and Mole- 
schott's ' Untersuchungen,' 10, p. 280. 
§^ ' Recherchcs sur les Mouvements Reflexes,' p. 48. Paris, 
1863. 
