No. 3-] STUDY OF STENOSTOMA LEU CO PS O. SCHM. 289 



than as processes of these cells. These facts indicate that the 

 fibres making the apparent network of the commissure are con- 

 tinuous with the processes of the ganglion cells, and that the 

 fibres are the true nervous substance of the commissure. 



There are three possible arrangements in which this nervous 

 material might be placed in order to give the appearances which 

 are found in both cross and longitudinal sections : (i) the ar- 

 rangement in tubes as Nansen has described them, (2) the 

 arrangement into a true network according to the theories of 

 Bohmig, Rawitz, and Leydig, and (3) the arrangement into a 

 feltwork of independent fibres which cross one another at an 

 infinite variety of angles, but which do not anastomose to form 

 a network. 



The sections do not uphold the first supposition, in that the 

 apparent network obtained in cross-sections appears very irreg- 

 ular and broken in many places. In longitudinal sections the 

 fibres have the appearance of starting from the small processes 

 of the ganglion cells. It is not probable that these processes 

 enlarge and become hollow tubes as they proceed from the 

 ganglia toward the median line of the body. 



In focusing upon this apparent network it has not been pos- 

 sible to make out whether the fibres unite with one another to 

 form a genuine network, or whether they merely cross one 

 another so as to make a feltwork. In longitudinal sections of 

 the commissure it may be seen that the apparent network is 

 more pronounced at the centre of the commissure and also 

 near the median line of the body. At the ganglia a network is 

 scarcely visible, but nearly parallel fibres may be seen to run in 

 small groups in different directions into the ganglia. Lines 

 running from the ganglia in the direction taken by some of these 

 fibres would converge to a point somewhere between the ganglia. 

 If this apparent network be conceived to be made by the cross- 

 ing of independent fibres which run in all directions from that 

 part of the surface of one ganglion which comes in contact 

 with the commissure to that part of the surface of the other 

 ganglion which is in contact with the commissure, the appear- 

 ance would be given in longitudinal sections of the commissure 

 of nearly parallel fibres, or of a very slight network, at the 

 ganglia, while the most pronounced network would be found 

 near the median line of the body. In cross-sections of the com- 



