PROTOPLASM 23 



as regards the growth of nerve fibres from cells. Burrows (1911, p. 63) 

 extended the method to the chick embryo, and Carrel and Burrows (1910) to 



thr 



46* hours 



FIG. 20. GROWTH OF NERVE FIBRES IN CLOTTED LYMPH. Medullary cord tissue of 

 embryo Rana palnstris, 3 "3 mm. long. Lymph from Rana pipiens. 



7. Apparently single fibre (/) growing from a pointed cell (c<j) which projects from a mass of cells (ma). One 



day after isolation of tissue, 28th April 1908, 12.25 P.M. 



8. Same fibre, 2 P.M. Now seen to be double. 



9 Same group of fibres, 10.25 P.M. Four distant fibres (nf\ 71/4) now visible. Fibrin filaments (thr) were also 

 present in the earlier stages, but omitted in sketches. 



10. Same group, 29th April, 11 A.M. r>/ 5 possibly a branch of nf\. 



11. Same group, 10.30 P.M. Continuation of Ji/j and upper branch of >/a unfortunately left out of sketch. Note 

 migration of cell ct.^. Identity of other isolated cells uncertain. 



Total interval between first and last figures thirty-four hours. 



(Ross Harrison, 1910, PI. 2, figs. 7-11 ; Jf. Exptr. Zoology.} 



