TRANSPLANTATION OF CEREBRAL CORTEX 569 
apex of the triangle extended downward. The time consumed 
in the transfer of the cortex was made as short as possible. In 
the earlier operations the lateral ventricle was often accident- 
ally opened, although the intention had been to remove and 
replace a thin superficial portion of cortex only. The appar- 
ently successful cases were found to be those in which the 
ventricle had been opened and a bit of cortex had become ad- 
herent to the choroid plexus. During and after the operation 
the dura was preserved if possible but in rats of ten days the 
cerebral membranes are very delicate and difficult to differ- 
entiate from one another. Sometimes the dura remained con- 
veniently attached to the cartilaginous flap. After trans- 
ference of the cortical mass the cartilaginous flap was freed, 
the skin drawn over it and the edges of the skin retained in 
proximity by a collodion dressing. 
Attention to a number of details was found to be advanta- 
geous. Complete anaesthesia before and during the operation 
was found necessary, otherwise the struggles of the animal 
caused protrusion of the cerebral substance through the incision. 
Asepsis was secured by using successive sets of sterile instru- 
ments. No antiseptic was used other than the ether of the 
collodion dressing. Maintenance of the body warmth both dur- 
ing and after the operation was essential. This eare for the 
maintenance of the body heat and that for the exclusion of anti- 
septics were the very helpful suggestions of Prof. C. 8. Sherring- 
ton, who was a visitor to the laboratory during the early experi- 
mental period. Care was exercised not to injure adjacent cere- 
bral structures. Transplanted material was handled rapidly 
and with a warm knife. An almost insuperable difficulty ap- 
peared to be that of retaining the transferred material in the 
desired place. At ten days of age the cerebral cortex of the 
albino rat is soft and plastic. The removal of tissue leaves an 
irregular and almost imperceptible cavity, so that the trans- 
ferred tissue is displaced almost immediately from the con- 
vexity of the cerebral hemisphere. In the later series an at- 
tempt was made to permit the formation of a thin blood clot 
lying over the transferred bit of tissue and extending to the 
