SPINAL CORD REGENERATION. I 475 
proved by the fact that they contain neurofibrillae which are 
readily seen in sections stained with Held’s hematoxylin or 
toluidin blue. The fibers arising from the anterior portion of the 
cord pass caudad and dorsad, those from the posterior piece 
cephalad and dorsad. This deflection from the straight course 
is necessitated by the interposed mass of notochordal sheath 
tissue, which it is seemingly impossible for the nerves to pene- 
trate at this stage. The number of fibers from each end of the 
Fig. 2 Sagittal section of an embryo killed 2 days after operation. The 
epidermal ingrowth is partially withdrawn. Both spinal cord and notochord 
are divided and short nerve fibers are developing from each piece of the cord. 
The tail is not shown in the figure. (Embryo VIII 67, 3-12). 
Fig. 3 From the same embryo as the preceding figure. The notochord(N.C.), 
the mass of notochordal sheath tissue (V.C.S.), the epidermal ingrowth (£.I.), 
the anterior (S.P.A.) and posterior (S.P.P.) pieces of the spinal cord, and the 
motor nerve fibers (V.F.) growing from each end of the latter areshown. (Embryo 
VIII 67, 3-18). 
spinal cord is small, varying from five to fourteen in the different 
embryos. Their course is in all cases irregular. At first they 
pass either caudad or cephalad, according to the end from which 
they rise, then turn and apparently follow along the outside 
of the notochordal sheath tissue. Though their course is tortu- 
ous, they are directed toward the opposite end of the spinal cord. 
The longest fiber observed measures 63.75 » in length. In no 
case are any of the normal peripheral nerves deflected from 
their course toward either end of the cord. 
From the evidence afforded by the sections, it would seem 
that the increase in length of the spinal cord has not kept pace 
