Structure and Polarity of Electric Motor Nerve-Cell in Torpedoes. 223 



living cell it can in no way be considered as the network or thread-like 

 structure that we find supporting the nucleolar bodies after fixation. 

 I think this is easily proved by the following facts : In torpedoes Nos. 

 20 and 4 the peripheral cells in control specimens show a centrally 

 placed or ventrally oriented plasmosome and the accessory nucleoli 

 distributed throughout the cell. It is evident, upon inspection of the 

 drawing and preparations, that in that condition, and given the pres- 

 ence of such a fine-meshed network, the plasmosome and accessory 

 nucleoli could not be moved without breaking all the meshes and 

 threads through which they had to pass. And yet in figure 23, plate 5, 

 from gravity experiment on torpedo No. 4, all these bodies are shown 

 down on one part of the nuclear membrane, while the entire remainder 

 of the nucleus is occupied by the well-fixed, fine-meshed alveolar 

 reticulum. It must be true that the reticulation of the achromatic 

 material is a result of fixation and that, while living, the nucleolar 

 bodies can move or be moved through it without injuring its structure. 

 On the other hand, too, in cells subjected to a stronger current of elec- 

 tricity (over 0.25 ampere) the various substances that are moved to the 

 anode leave a thread-like reticulum that may be fairly considered to 

 be a part, probably in some slightly changed condition, of the original 

 structure of the nucleus. 



Of course it would be possible to have a reticulum, or better an alveo- 

 lum, through which the plasmosome might move as a wet marble could 

 move through soapsuds or foam. But in this case the alveolar struc- 

 ture would undoubtedly show in life, which is not the case in this nerve- 

 cell. Such a condition has been suggested by Murlin (27). 



Further, it would be hard to determine how far and to what degree 

 this material enters mechanically into the other structures of the 

 nucleus. There is reason to believe that it is denser and firmer where 

 it holds together the cloud of perichromatin around the chromatin 

 particles, for under several circumstances this gathering of material 

 moves as a unit and independently of the other similar clouds and other 

 structures of the nucleus. Here it appears to have a radial arrangement. 



The differences in the reticulum as found in different parts of the 

 same preparation are in themselves of great interest. In figures 22 

 and 23, plate 5, are drawn two cells, one from a Bouin fixation and the 

 other from a Flemming fixation, showing how the appearance of this 

 achromatic substance differs according to the distance the fixative has 

 had to penetrate in order to reach it. This difference also comes out 

 in figures from different preparations, and where one has studied many 

 preparations he can at once say about how far from the surface the 

 fixative had to penetrate to get to each cell. 



A proper fixation of the nucleus of these nerve-cells is a fairly difficult 

 matter and many papers on the subject (otherwise excellent) show 

 figures that indicate much deficiency in this respect. And this is aside 



