Irving Hardesty _ 103 
With the exception of those accompanying the blood-vessels, the pia 
mater sends but few ingrowths into the white substance and these are 
very delicate. Many nuclei are present which, without doubt, enter 
the spinal cord from the outside, and are therefore mesodermal in origin 
but whether any of these take part in producing neuroglia is difficult 
to determine because a neuroglia cell may not be designated as such till 
is acquires certain characteristics. 
+ 
(Nore.—In Dr. Hardesty’s original drawing for Fig. 1 the black neuroglia fibers of 
the marginal veil appear in a transparent, white area invaded by a few faint strands 
from the pia. The half-tone reproduction here shown fails to give the desired con- 
trast, since the screen carries considerable color into the marginal veil, confusing 
this somewhat with the gray pia which lies immediately outside of the black felt- 
work of neuroglia fibers. — ED. ] 
