600 THE NERVE CELL. 



character have been made by Mann upon the motor nerve cells of the 

 brain and spinal cord, and the nerve cells concerned in visual percep- 

 tions (in the retina and the occipital lobe). Hodge did not examine the 

 condition of the Nissl bodies, but notes that active nerve cells, as 

 compared with those at rest, show a diminution of volume and a 

 lessened power of reducing osmic acid, the nucleus also becoming 

 shrunken and showing a tendency to stain more deeply. Vas 1 and 

 Lambert 2 described the stimulated nerve cell as becoming clear in the 

 centre and chromophil towards the periphery, and Pugnat 3 found 

 that, with more prolonged stimulation, the Nissl bodies disappear 

 entirely. Mann described the cell body and nucleus as becoming at 

 first somewhat enlarged as the result of activity, but with fatigue 

 there succeeds diminution in bulk of both nucleus and protoplasm ; he 

 also noted a diminution in the chromatic substance of the cell proto- 

 plasm. Nissl 4 himself, in repeating these experiments, was unable 

 to obtain such marked results. 5 Nevertheless, it appears clear that 

 the effect of activity is to induce certain chemical changes within 

 the body of the nerve cell, its functional activity being attended 

 with a diminution in the amount of chromatic substance in the cell 

 protoplasm. 



Much more definite effects are obtained as the result of section of 

 the nerve fibre process. The first study of these effects we also owe 

 to Nissl; 6 his observations have been confirmed and extended by 

 many others, and especially by Lugaro, 7 Marinesco, 8 and v. Gehuchten. 9 

 Their results may be briefly summarised as follows : When a motor 

 nerve is cut, the cells from which its axis cylinders are derived begin, 

 within from twenty-four to forty-eight hours after the lesion, to show 

 indications of chromatolysis. The granules of Nissl become less defined, 

 and the neighbouring portions of the protoplasm diffusely coloured. 

 Concomitantly with, or soon after this, the cell body becomes 

 swollen and the nucleus is often displaced to one side. This process 

 goes on for about fifteen days, at the end of which time most of 

 the cells of origin of the nerve are converted into rounded bodies, 

 staining nearly uniformly with methylene-blue and showing no Nissl 

 granules or only small ones, and these confined to the periphery of the 

 cell. The change begins apparently at the place where the axis 

 cylinder leaves the cell, and invades first the perinuclear portion of the 

 protoplasm, and then its successive layers, the peripheral being last 

 affected. It also extends gradually into the dendrons. After fifteen 

 to twenty-four days the process of chromatolysis is at an end, and a 

 process of reparation begins ; this proceeds very slowly, so that it may 

 take three months to be completed. At the end of that time the cells 

 have for the most part resumed their original appearance, even although 

 the cut nerve may not have undergone regeneration. 



1 Loc. cit. 2 Compt. rend. Soc. de bioL, Paris, 1893. 



3 Com2)t. rend. Acad. d. sc., Paris, 1897, tome cxxv. p. 736. 



4 Ally. Ztschr.f. Psychiat., etc., Berlin, 1897, Bd. liv. 



5 Nor did Eve, working with the rabbit's sympathetic. Journ. PhysioL, Cambridge 

 and London, 1896, vol. xx. p. 334. 



6 Ally. Ztschr.f. Psychiat., etc., Berlin, 1892, Bd. xlviii. S. 197 ; CentralU. f. Ni-rrculi. 

 n. Psychiat., Coblenz u. Leipzig, 1894, S. 337. 



7 Riv. dipatol. nerv., Firenze, 1896 ; Sperimentale, Firenze, 1895. 



8 Prcsse med., Paris, 27 Janvier 1897 ; and Rev. gen. d. sc. pures et appliq., Paris, 30 

 Mai 1897 ; also in Arch. f. PhysioL, Leipzig, 1899, S. 89. 



9 Cellule, Lierre et Louvain, 1897, tome xiii. 



