122 



GEORGE FRED SUTHERLAND. 



regenerated tail plus a second fourth of the normal tail was 

 removed and put immediately into Gilson's killing fluid. The 

 times of killing were as follows: normal, immediately after the 

 operation, i, 3, 5^, 9^, and 14 hours, and i, 2, 3, 4, 6, 8, 9, 10, 

 12, 14 and 16 days after the operation. Usual methods of 

 technique were followed. Delafield's haematoxylin and acid 

 fuchsin stain the nuclei blue and the cytoplasm pink, but do not 

 distinctly bring out cell boundaries. For the most part sections 

 were made in the sagittal plane. 



III. Observations. 



The study was confined to the histology of regeneration in the 

 spinal cord, since a preliminary examination showed that this 

 organ of all those in the tail was best adapted for a study of the 

 present problem. Fig. 2 shows by a sagittal section the spinal 



^ 



;'.':-^ 



NTC 



Fig. 2. Sagittal section through a part of the normal tail, showing the spinal 

 cord and its relation to the surrounding tissues, nc, spinal cord; cc, central canal; 

 ntc, notocord; ct, connective tissue; pc, pigment cell. (330 diameters.) 



cord, and its relation to the surrounding tissues. Fig. 3 shows a 

 transverse section of the spinal cord alone. It is a hollow tube 

 which distally is formed of a single layer of cells. The nuclei are 

 very near the inner border of the cells so that there is a wide 

 outer zone of cytoplasm but practically no inner cytoplasmic 



