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GEORGE FRED SUTHERLAND. 



stimulus of the operation are contracted or compressed, or cut 

 nuclei which have rounded off. These deeply-staining nuclei, 

 whether rounded or irregular in shape, are smaller than normal 



Fig. s. Sagittal section through the side of the spinal cord immediately after 

 the operation, showing the deeply-staining nuclei at the cut end. dn, deeply- 

 staining nuclei. (920 diameters.) 



nuclei, so it may be that the chromatin, which stains deeply, is 

 condensed on account of the loss of achromatic material. 



The same assumption is borne out by the somewhat different 

 appearance of nuclei in the tadpoles killed one hour after the 

 operation (Fig. 6). Some are rounded as before; others are 

 angular or slightly hour-glass shaped, with rather dense cyto- 

 plasm extending out from the corners. If parts of the nuclear 



Fig. 6. Sagittal section through the spinal cord one hour after the operation. 

 This shows the "contracting" nuclei, cc, central canal; dn, deeply-staining nuclei; 

 nn, normal nuclei. (920 diameters.) 



membrane were held by the cytoplasm while the nucleus as a 

 whole decreases in volume either by contraction or loss of achro- 

 matin, the nuclei might present such an appearance. Moreover 

 there are gradations from hour-glass-shaped to normal nuclei 



