Irving Hardesty — 87 
but seldom exceed 1 # in breadth. The fibers are of unknown length. 
Short fibers are common, but they are undoubtedly pieces, cut by the 
knife. Frequently in the thicker sections one fiber may be traced intact 
through the domain of two or more neuroglia cells (Fig. 3, &) and then 
the ends appear as cut by the knife rather than as terminations of the 
fiber. Anastomosis is to be observed but not as a very frequent occur- 
rence. Both transverse and longitudinal sections of the specimens dis- 
tinctly show many fibers obliquely and transversely cut, in fact cut in 
all conceivable planes. The fibers run tortuous courses in the inter- 
axone spaces of the white substance or form a general complex plexus 
in the gray. They may be seen to form loose feltworks about the 
medullated axones often quite closely investing the medullary sheaths, 
the membranous portions of which stain a pale red in contrast. Gen- 
erally, however, they seem to merely course freely in the spaces among 
the nerve fibers showing a preference for none. Comparing the trans- 
verse section with the longitudinal, it is immediately evident that while 
the fibers course in all planes, more have a tendency to course in the 
direction of the nerve fibers than transversely to them (Fig. 4). They 
show no fixed relation to the neuroglia nuclei, merely running indiffer- 
ently in the spaces occupied by them. 
In the gray substance the neuroglia fibers either do not hold the 
stain so well or are less abundant than in the white substance. While, 
as Aguerre noted for the human spinal cord, they are abundant in the 
commissura alba posterior and in the substantia grisea centralis, they do 
not show so abundantly through the general gray figure as one would 
expect. Occasionally areas may be noted quite rich in neuroglia fibers 
but these are more often in the vicinity of the blood-vessels. Though 
the periphery of the columna posterior is rich in well-stained neuroglia 
fibers, the column itself, which contains a great amount of substantia 
gelatinosa, appears as a brownish-red, compact granular mass filled with 
innumerable nuclei, most of which are of the small deeply-staining 
variety. Neuroglia fibers can scarcely be distinguished except about 
occasional blood-vessels and entering nerve fibers. What are supposed 
to be neuroglia nuclei are more abundant in any given area of the gray 
substance than of the white as is to be expected because in the former 
they are less dispersed by the presence of medullated axones within it. 
On careful examination the oil immersion reveals many fine fibers in 
the gray substance but these are pale red in color. The preparation 
gives the impression that if these are neuroglia fibers their staining 
properties have been influenced by some other tissue constituent in 
which they are imbedded. Throughout-the entire gray figure many 
