TRANSPLANTATION OF CEREBRAL CORTEX Di 
ten per cent formalin. Some weeks before the brains were to 
be embedded for cutting, they were mordanted in toto in 
Miiller’s Fluid. The blocked material was cut serially either in 
thirty or forty-five micra sections and stained by the Weigert- 
Pal method. Alternate sections were counter-stained with 
Upson’s Carmine. 
The sections were studied individually under low and high 
power. 
I am indebted for the drawings to Miss Katherine Hill and 
Mr. A. B. Stredain. 
The completion of this study was made possible through the 
courtesy of Dr. R. R. Bensley and Dr. C. J. Herrick, who granted 
me an additional amount of free time for the microscopical 
study of the sections. 
The rats used were bred in the laboratory, with the exception 
of Series IV, Group I, for which I am indebted to Dr. J. B. 
Watson. 
THE FINDINGS FOR CEREBRAL TRANSPLANTATION 
The investigation now reported was undertaken for the pur- 
pose of determining the possibility of maintaining the life of 
nerve cells in bits of transplanted cerebral cortex. This con- 
tinuity of vitality has been found possible and growth has gone 
on in the neurons transplanted. The neurons which have sur- 
vived have assumed their morphological relations to other neu- 
rons within the transplanted bit. The growth changes within 
the transplants are very similar to those of normal material of 
about the same age. Medullation is fully accomplished. ‘The 
number of medullated fibers is however relatively smaller than 
in normal material but this is probably due to the absence of 
such fibers as grow into any cerebral region from other parts 
of the brain. The growth of the individual neurons has been 
very considerable. Watson, 03, found that the cortex of the 
brain of the albino rat is but slightly developed at the tenth 
day of life, the age at which transplantation was attempted, 
and that medullation appears much later. The transplanted 
neurons must therefore have been very immature. 
