Ranson, F2bers in Leszons of the Brain. 203 
each other occurred in all but the oldest rat. In rats Nos. 2, 
3 and 4 it was found that the parts of the cortex had altered 
their relative positions in the same manner, such that if we 
consider the under surface of the cortex as stationery the cor- 
tex upon the upper surface shifts lateralward over the splenium, 
Fig. 3, and medialward in the posterior part of the occipital 
lobe, Fig. 2. This is explained by the fact that when a large 
number of fibers develops in any area, that area increases in 
size more rapidly than the surrounding parts. in Fig. 3 is seen 
a dense area of fibers just medial to the scar, which is respon- 
sible for the lateral displacement of the scar. 
(5). We have seen that atthe center of stab wounds, 
where every fiber must have been cut by the knife, medullated 
nerve fibers may be traced across the wound and into the norm- 
al brain tissue on each side. While there can be no doubt 
that these are new formed elements, they represent in all prob- 
ability not vegenerated but entirely new axons. The number 
of such fibers is very great in the youngest rats, but decreases 
quite rapidly as the age of the rat at the time of the operation 
increases. Unfortunately the brains of rats operated on ata 
more advanced age were spoiled in the process of hardening, 
and I cannot say at what time the brain of the rat ceases to 
have the capacity of sending fibers across the site of the lesion. 
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