( 21 ) 



not yet to be explained more tully (cells of the nucl. ventralis acustici 

 which degenei'iite after lesion of the peripheral octavus). 



The method which 1 used in opeiatinfj,' on full-grown animals is 

 preferable, in so far as it, in general, leaves no room for doubt, at 

 least about the comiectiou between the cut tibres and the degene- 

 rating cells. 



Where, moreover, the corte.x, cerebri, examined in series of sections, 

 nnifonnly lacks cells which are present in uuoperated animals, these 

 cells must be regarded as elements of origin of cut iibres of the 

 corpus callosnm. 



A second maxim in estimating the cell degeneration after culting of the 

 axis-cylinder is that a total even temporary "disappearance" ofthe cells of 

 origin is not to be expected, when importani collaterals arise between 

 the place of the lesion and the cell of origin of the axis-cylinder. It 

 may thus be assumed that no other cellulifugal fibres are connected 

 with the degenerated cortex nerve cells outside the corpus callosum. 

 The nerve cells in the cortex cerebri which cannot i)e made visible 

 are contined to the subgranular pyramidal layer (lamina V Brodmann). 

 The only lesion which might influence the cells of the hemispheres 

 examined b}' Nissl's method is, in the operation performed, exclusively 

 the cutting of the callosum, in which the injury to the cortex might 

 have to be included, which latter, however, could only influence by 

 means of the callosum-elements of the side examined. The last 

 is the case only in the operation of rabbit 16, in which animal but 

 a part of the cortex was removed. From the above, therefore, we 

 may deduce without doubt that the said sub-granular pyramidal cells 

 give origin to the callosal fibres. 



The examination showed, moreovei', that alterations of a less serious 

 nature occur in various layers, viz. changes in the cell-bodies them- 

 selves, — where a judgment on degeneration or approaching recovery 

 could not be pronounced with certainty ; — and further a loss 

 of intercellular molecular matter and a massing of active glia-elements. 



Experiments performed in other parts of the nervous system prove 

 that cutting the axis-cylinders has likewise an influence on the cells 

 of origin, when important collaterals are given oif by the axis-cylinder 

 between the place of the lesion and the mother-cell. The changes 

 which are then met with in the cell body are of a temporary nature 

 and disappear wholly or partially after some time '). This period of 



1) It is known thai the gigaulo-pyramids of region 4 (motor zone! disappear 

 when the pyramid tract is previously cut. Tins suggests strongly that callosal 

 fibres which begin in this region liave their origin in other cflls than the giganto- 

 pyramids. 1 hope to be able to prove this shortly by means of other material. 



