82 S. E. JOHNSON AND M. L. MASON 
wholly of non-medullated fibers, there appearing only about 150 
small medullated fibers, scattered irregularly over the field of 
a cross-section. 
In a cross-section of the white ramus we counted a total of 
1252 medullated fibers of various sizes from approximately 1.54 
up to 16.94. The results of a differential count may be tabulated 
as follows: 
Ac OpOT LESS erie ee one a ees rr Ee ES Oe ete ae 422 
DIPS Psa iON PCa es | aa OR RE ane en oe Coe ee WO RAS ORT Ne aii an tt Mewes 506 
SLU TAM KO} URS G) Pie Seeuehe es pee nen tee Pee Reh gh Rr ORG arab Ae Ame Sete tp 151 
DOM ALO EO Oiarg. pote see ob oece Br tpey Sen e hk Sri PEA By VATE OO REE Pea as 40 
ca! ADAGE N27 err ysan cscaey A UET SUS BGM nS ea Reve nT tee ee ea 74 
DAG OMI Bis 3. deotrarte eee cusee so POT Oe oO EL EO ee eae 35 
Joey HO) IRON G6 oa dacoes Ps ike Ie et is ii MEIN Grn any ciomnts Cito e 10 
IS TPA STO) HD UT esr eee ee eS AN) 4 Pe eRe Erneta inet Sete EEE I 13 
Dalit OWN: Deco aero Susy aie) coeae See ugh oS eee tceeae FO A eRe ee sR il 
OLAS, Joes ahi bs acts Soe ee reeds fre RO OC CR ne 1252 
In the above tabulation of fibers the feature that stands out 
most prominently and unexpectedly is the presence of such a 
relatively large number of sensory fibers. It will be noted that 
there is an abrupt diminution of fibers of sizes between 5.6 and 
7.du. The fibers of this size and under are undoubtedly of two 
types (Ranson and Billingsley, ’18), visceral efferent (the major- 
ity) and small afferent fibers. These cannot at present be differ- 
entiated microscopically. The remaining 193 fibers range from 
5.6 to 16.94, and probably all of these are afferent fibers. Two 
hundred (approximately 16 per cent) would be a low estimate 
for the total number of afferent fibers in the ramus. As shown 
in figure 5, many of the large medullated fibers are grouped in 
definite fascicles. It will be a matter of the greatest interest 
to trace out the course and distribution of these well-defined 
bundles of large medullated fibers. 
The rami of the laboratory specimens shown in figures 1 to 4 
were run through various fixing solutions, stained in iron haema- 
toxylin, and sectioned, with the hope that we might be able to 
identify the white rami. This we found to be quite possible in 
the majority of instances. The nature of the rami is indicated 
