20 The Structure of Nerve-jibres. 



characteristically much thicker than the fibrils. The latter are always in 

 much smaller number in each unit length of the fibre. Other forms seen 

 far more frequently are short ovoid and spherical granules and flakes of 

 the precipitated dye. When all these forms are present they occur in a 

 definite order. The fibrils are found in the first portion of this stained 

 region abutting upon the unstained anodal tract, then follow bacillar granules, 

 then ovoid granules always associated with tracts of the fibre in which 

 definite kathodal staining and coagulative changes are found. In this latter 

 region spherical granules may also occur, but they are placed not in the 

 central coagulum but in the clearer fluid surrounding it. In one and the 

 same portion of the kathodal region ovoid granules may be seen enclosed in 

 the central mass, flakes may be seen upon its surface, and spherical granules 

 may be seen in the clear fluid surrounding it. 



To understand the meaning of these granule formations and this difference 

 in their character, it is essential to remember the manner in which they 

 are thus associated with different degrees of coagulation. At the distal 

 extremity of the homogeneous anodal tract is placed the region in which 

 the first approach to visible coagulation takes place. In this place there 

 is no separation between a core and a surrounding fluid. Each unit of 

 volume still contains almost its normal amount of uncoagulated material. 

 The threads of coagulum are still surrounded by an almost normal intra- 

 myelin solution. It is in this region, where " solid phase " is still surrounded 

 by a great mass of " fluid phase," that the fibrils are sometimes seen. 

 Before I had puzzled out the meaning of the adjacent unstained anodal 

 tract, in which no granule formation takes place except as the result of 

 diffusion from the source of the injury current, I was greatly exercised by 

 this constant position of such fibrils as I had found. The bacillar granules 

 probably represent a further stage of degradation, in which, however, the 

 main mass of material is almost normally fluid in character. In both these 

 cases the dye is precipitated upon the outer surface of threads of coagulum. 



As we proceed into districts nearer and nearer to the kathode an opposite 

 set of conditions arises. The greater portion of the proteid material is 

 precipitated or coagulated as a " solid phase." Within the interstices of 

 this mass there are, however, entrapped collections of solution. It is 

 probable that here the granules represent such collections within which 

 the dye is precipitated. 



At one end of the scale of changes solid threads are stained upon their 

 surfaces. At the other there is a similar staining upon the surface of a 

 coagulated mass, and within this again are intensely stained vacuoles. 



In no place are neurofibrils of indefinite length existent, simply by reason 



