52 THOMPSON YATES LABORATORIES REPORT 
the various nerve-branches in the limb itself was carried out. Strict asepsis and profound 
anaesthesia were maintained throughout the operative procedure. 
In a certain number of experiments on motor distribution, the Walierian degeneration 
was employed : the segmental nerve, the distribution of whose motor fibres it was desired to 
investigate, was cut completely through just after its exit from the spinal dura as far proximal to 
its spinal ganglion as possible. A sufficient number of weeks was then allowed for the progress of 
the degeneration : this time varied from i8 days to 30 days. The animal was then killed and 
dissected. The nerve twigs to the muscles were fixed and stained with osmic acid and then 
allowed to dissociate in methyl alcohol 40 per cent, in water. They were then exhaustively 
examined in teased preparations. Eacli nerve twig was completely examined, i.e., the whole 
thickness ot it teased up, mounted and preserved in a series of preparations. The accuracy, 
delicacy, and ease of this method surprised me not a liule. It is greatly superior to the most 
perfect serial preparations of cross and longitudinal sections. 
General Remarks 
The IlIrd, IVtii, and Vlth cranial nerves are distributed to muscles, and to these muscles 
probably distribute afferent nerve-fibres.* In regard to cutaiieous sensation, these cranial nerves, 
as also the Vllth, Vlllth, IXth, Xlth, Xllth, together with the sub-occipital nerve, now often 
called 1st cervical, can be left out of consideration : they possess no sensory skin-fields whatever. 
All the other nerve-pairs possess each a sensory skin-field. In the description of the 
cutaneous fields, the terms employed in my previous communication t will be advantageous : of 
tliese a few special ones may be here defined : — 
Mid-dorsal line of the body. ^ Lines along which the median vertical longitudinal plane of 
Mid-ventral „ „ „ f the body attains the dorsal and ventral surfaces of the body. 
Lines on the dorsal and ventral surfaces of the limb, along 
which the skin-fields of the spinal nerves range themselves 
and behave as if at mid-dorsal (or mid-ventral) line of the 
body. These lines may be considered sideward extensions 
of the mid-dorsal and mid-ventral lines of the body into 
corresponding surfaces of the limb. 
Throughout this paper, anterior means toward the head, posterior away from the head ; 
tlie spinal nerve roots, therefore, which are in anthropotomy frequently styled anterior and 
posterior, are here spoken of as ventral and dorsal. 
The difficulty of obtaining suitable skin-points to serve as accurate and easily comparable 
indices of the absolute position of the sensory fields was mentioned in my previous paper.J In 
the head region, points of great value in this respect are furnished by the mouth and the pinna. 
In describing the distribution of the nerves under the heading of each nerve pair 
possessing a cutaneous field, I give first the result of some one experiment thought typical for the 
Mid-dorsal line of the limb. 
Mid-ventral „ „ „ 
* Sherrington, 'Journ. Physiol.,' Cambridge, 1894 (also ' Proc. Roy. Soc.,' February 26, 1897), 
t ' Phil. Trans.,' B, 1892, loc. cit. J liiJ. 
