196 JOURNAL OF COMPARATIVE NEUROLOGY. 
hardened in vAN GEHUCHTEN’S solution, imbedded in paraffin, 
cut in serial sections 6 » thick, and stained in erythrosin and 
toluidin blue. 
Results. 
It will be most convenient to give a general description of 
the wounds in each of the four animals, and to follow this with 
a summary of the more important points as they are seen when 
the four specimens are compared. It will be found that this . 
description differs from the usual accounts in the following 
points: (1) the absence of adhesions in the meninges, (2) the 
absence of a well defined connective tissue scar, (3) the 
atrophy of sectioned nerve fibers on the cell body side of the 
injury, (4) the distortion of the wound due to the shifting of 
areas in the growing cortex and (5) the presence of nerve fibers 
crossing the site of the lesion. 
Rat No. I was operated on when twenty-one days old and 
was killed fifty-three days later. The wound was found in 
the occipital region of the left hemisphere, parallel to, and near 
the middle line. On examining the serial sections of this 
region the wound could be traced from near the posterior edge 
of the splenium forward for a little over 2 mm. __In its anterior 
part it penetrates the cornu Ammonis and runs a slight distance 
into the thalamus. From this point the floor of the wound 
gradually slopes upward and backward until the surface of the 
cortex is reached. By reference to Fig. 1 the general charac- 
ter of the wound will be seen. It is visible asa light band 
running down from the surface of the cortex and extending 
just through the corpus callosum, but it does not at this point 
extend into the cornu Ammonis. Throughout its whole extent 
dark granular masses are apparent—the remains of unabsorbed 
blood. The scar tissue is quite abundant in this brain clearly 
marking off the wound from the normal brain substance. On 
comparing this preparation with a corresponding one ina set of 
serial sections of a normal rat brain, it was found that the bank- 
ing up of fibers on the medial side of the wound is not entirely 
the result of the operation, as an evident excess of fibers on the 
