566 ELIZABETH HOPKINS DUNN 
1909, Ranson reported successful transplantation of the spinal 
ganglion into the brain. Marinesco and Bethe had earlier 
transplanted ganglia to a position adjacent to the sciatic nerve. 
In these cases of successful transplantation the neurons remained 
alive. 
In 1904, while research assistant in the Neurological Labora- 
tory of the University of Chicago in charge of Professor H. H. 
Donaldson, I began some experiments in the transplantation of 
cortical cerebral tissue in young albino rats. 
MATERIAL SELECTED 
The albino rat was selected because of its adaptability as a 
laboratory animal. In contrast to the adult animals which had 
earlier been selected for attempted transplantation, a more 1m- 
mature animal was utilized. At the ninth or tenth day from 
birth the cerebral tissue of the albino rat is not mature, the 
hairy coat is not sufficiently developed to interfere with opera- 
tion, and although the young must be left in the mother’s care 
after the operation, they are not given that assiduous care 
which renders operation on very young animals so difficult. 
It is possible to return the operated young to the nest without 
fear of attack upon them from the mother, if the precautions 
mentioned under the discussion of methods of operation are 
observed. 
The records show that in all forty-six rats were operated. 
Two of these rats died soon after operation. Nine other brains 
showed nothing of interest on macroscopical examination. 
Thirty-five brains were sectioned and studied. 
For purposes of tabulation as appears in table 1, the forty- 
six operations are divided into four series made up of an irregu- 
lar number of groups. The term group had a definite connota- 
tion and marked the number of animals operated at one time. 
A group usually consisted of the young of one litter, the trans- 
plantation being made from one to another young rat of one 
litter. The brains were thus equally mature at time of opera- 
tion and the rats of the closest consanguinity. It was hoped 
that these two points might have weight in the preservation of 
