INGBERT, Cutaneous Innervation in Man. 211 
efferent fibers in them does not differ sufficiently from that in 
other peripheral trunks to modify our result. 
I. Estimate Based on Stilling’s Results. According to 
STILLING (1859) there are in man, in round numbers, 500,000 
nerve fibers in the dorsal roots of the spinal nerves of both 
sides, and 300,000 in the ventral. We therefore take from 
500,000 fibers a number equal to two-thirds of 300,000, or 
200,000 fibers, in order to add these to the efferent fibers in the 
muscular nerves. This leaves 300,000 or 60% of the nerve 
fibers of the dorsal roots to innervate the dermal surface of the 
body. If these data were correct, as unfortunately they are 
not, we could conclude that about 60% of the afferent fibers in 
the dorsal roots of man are cutaneous, i. e., go to innervate the 
dermal surface of the body, and about 40% go to the muscles. 
In the 60% credited to the skin there are included the fibers 
which pass to the viscera by the vam communicantes and recur- 
rent nerves, if any, but so far as we know, the number of these 
is small, and, for the present purpose, may be neglected. 
2. Estimate Based on Voischvillo’s Results. Another 
calculation on the relation of the cutaneous and the muscular 
nerve fibers in the dorsal roots of man can be made from the 
results of VoIscHvILLo (1883) and those by myself. Vorscu- 
VILLO sectioned the peripheral nerves in man at the places 
where they divide into cutaneous and muscular branches. The 
material used by him was hardened by 1% osmic acid and pre- 
served in g5% alcohol. The areas of the cross-sections of the 
nerves (of which I can find no record) were obtained by two 
methods, (1) by dividing the volume (determined by weighing) 
of a piece of nerve by its length, (2) by projections of the 
cross-section made by means of a camera lucida. 
In estimating the number of fibers in a peripheral nerve 
VoIscHVILLO counted all the nerve fibers of the section of the 
nerve that could be seen within a certain number of the squares 
of the ocular micrometer, and from this result he estimated the 
number in the entire cross-section. 
VOISCHVILLO’S average for the number of nerve fibers in 
the cutaneous nerves derived from the brachial plexus of one 
