48 Studies on the Neuroglia 



"A method which colors by precipitation is a priori incapable of giving 

 US the information which we require ; it must of necessity be confusing 

 in its pictures of structural detail." 



We may now turn our attention to the observations of investigators 

 who have employed a differential chemical stain in their study of neu- 

 roglia. Weigert, whose comprehensive work gave a new impetus to the 

 study of neuroglia, summarizes his results in the following statements: 

 " The neuroglia fibers, which have been hitherto regarded as processes 

 of Deiters' cells, differ chemically from the protoplasm of these cells. 

 This difference in the chemical constitution of the ' cell-processes ' is 

 apparent 'in the immediate vicinity of the cell nucleus, as well as at 

 some distance from it. The majority of the so-called cell processes are 

 not cell processes since two such apparent processes form a continuous 

 fiber, which is in no way interrupted by the cell body, as would be the 

 case were they true processes arising individually from the cell body. 

 In a word, there is no question here of cell processes or cell extensions, 

 but of fibers which are fully differentiated from the protoplasm.'' Wei- 

 gert describes two types of nuclei of neuroglia cells — large, vesicular 

 nuclei the chromatin of which has a granular appearance, and smaller 

 ones in which the chromatin forms a deeply-staining, homogeneous 

 mass, with transition forms between the two varieties. The large vesi- 

 cular nuclei often show a definite relation to the neuroglia fibers, in 

 that they form centres, over which and around which the neuroglia 

 fibers pass, simulating in a most characteristic manner the astrocytes 

 of other investigators. Numerous free neuroglia cell nuclei, notably 

 of the smaller, deeply-staining variety, which bear no special relation 

 to the neuroglia fibers, are also found, 



Mallory, working with his own method, obtained results which were 

 practically identical with those obtained by Weigert. Although these 

 'two investigators worked independently, their results were published 

 almost simultaneously. Pollack in a short note confirms Weigert's 

 statements and calls attention to the importance of his differential 

 neuroglia stain and the results obtained. Aguerre, after discussing 

 the recent neuroglia literature and calling attention to the superiority 

 of Weigerfs neuroglia stain and corroborating his observations, dis- 

 cusses at some length the shape and structure of the neuroglia cell 

 nuclei as found in the human spinal cord, stating that these nuclei 

 vary much in shape and size and are often polymorphous. He classi- 

 fies the neuroglia cell nuclei according to their size as follows: (1) 

 small nuclei, 3// to 4/^, to which variety the small deeply-stained nuclei 

 belong; (2) medium-sized nuclei, G/x to S/i, the smaller nuclei of the 



