332 THOMAS J. HELDT 



intimate blending and so a single double-staining reticulum 

 results. This single reticulum extends throughout the entire cell 

 and even beyond (fig. 5), and thus becomes directly continuous 

 with the pink-staining extracellular network previously described 

 under the observations on the stained smear as a whole. In 

 these cells there is of course a complete obliteration of the Nissl's 

 bodies as such. Thus, to repeat, it appears quite evident that 

 the intracellular networks are directly continuous with each 

 other, and again, are similarly continuous with the network 

 formed in the cellular interstices. These last changes described 

 may be called the final form the networks assume, for the appear- 

 ances just described are quite constant and do not change to 

 any noticeable extent in a temperature range of 20° to 30° ( —40° 

 to — 60°C.). It cannot be said that any of the appearances 

 described have an absolutely definite temperature at which they 

 appear. For instance, the last forai described may even be found 

 to a certain extent in smears frozen at — 15°C., none of the 

 earliest forms, however, occurs as a rule at temperatures below 

 -25°C. 



The significance of the networks described above and their 

 relation to Mollgaard's reticulum or ' glia-network' will be dis- 

 cussed later. 



ADDITIONAL OBSERVATIONS 



The perivascular network described by Mollgaard may also be 

 satisfactorily studied in the foregoing preparations. Its origin 

 is plainly from the chromatin of the nuclei of the endothelial 

 cells of the blood and lymph capillary and precapillary vessels 

 (fig. 6). The variations and various relations of the network 

 merit no description. The chromatin of the nuclei of the glia 

 cells also form networks but their relation to both the networks 

 of the nerve cells and the perivascular networks seems to be 

 merely one of accident. The rather constant appearance of what 

 Mollgaard believes to be a glia cell at one pole of the nerve cell 

 nucleus the author did not observe and it is probably explained 

 as being a modification of a chromatin nuclear cap. 



All the observations on frozen neural tissue apply to smears 

 frozen and fixed as soon as thirty-two seconds after decapitation 



