380 M‘CARTHY ON SPINAL GANGLIA. 
persistence of an embryonal condition, and that where there 
are few nuclei the embryonal cells have become transformed 
into connective tissue of a fibrillar character. To me, on the 
contrary, it appears more probable that the larger number of 
nuclei are the result of proliferation of previous nuclei. See 
figs. 1 and 11. 
The nerve-fibres run in a very irregular manner through the 
ganglion, so that a section of the ganglion shows the fibres 
cut, some transversely, some obliquely, and some longitu- 
dinally. Ranvier’s constrictions in the sheath of Schwann 
can be very distinctly seen, and the nuclei often appear more 
within than in this sheath (cf. Mayer’s observations). The 
medullary sheath appears to be composed of small rods 
radiating from the axis cylinder to the sheath of Schwann. 
The arrangement of these rods, as seen in transversely cut 
nerve-fibres, is not always the same. In some the entire 
space between the axis cylinder and the sheath of Schwann 
is occupied by these rods, while in others the rods appear 
shortened, and also compressed laterally into bundles im- 
bedded in some homogeneous substance. Again, in longitu- 
dinal sections, the appearance varies according to the place 
of section. If the section has passed exactly through the 
centre of the fibre these rods appear in a regular line and at 
right angles to the axis cylinder; but if the section has 
not passed through the centre, then these rods, being cut at 
various angles, produce a cloudy or stippled appearance. 
Reference to the accompanying illustrations, for the very 
beautiful and accurate drawing of which I am indebted to 
the kindness of Dr. Klein, all enable the reader to better 
understand my description. 
The regularity of the arrangement of these rods, as seen in 
some longitudinal sections of nerve-fibres, is very suggestive 
of the appearance of striated muscle. In i Sydenham 
translation of Stricker’s ‘Histology,’ vol. i, p. 161, Dr. 
Grandry is said to have observed in naked axis cylinders, as 
well as in those enclosed in a medullary sheath after treatment 
with nitrate of silver, fine transverse striations of such regu- 
larity as to remind the observer of the structure of striated 
muscle. If this description be correct, it cannot refer to the 
structure which I describe, which is most unquestionably im 
the medullary sheath. Lautermann (‘Centralbl., f. d. Med. 
Wissensch.,’ No. xlv, p. 706, 1874) is inclined to agree with 
Stilling in regarding the medullary sheath as composed of 
small tubules, and then makes very brief allusion to rod-like 
bodies, such as I describe, seen by him in osmic acid 
preparations. Reference to the descriptions and illustrations 
