No. 2.] CHANGES lAT NERVE CELLS. loi 



(2) Conversely, a cell becomes specialized to perform a certain 

 function only by an increased growth of certaiti of its parts. 



Thus reproductive tissue is most richly nucleated. Possibly- 

 even more richly nucleated is cellular nerve tissue. In gland 

 tissue, nuclei are quite prominent ; but the characteristic of a 

 gland cell is its granulation. From a red blood corpuscle the nu- 

 cleus may be entirely lacking ; the reticulum, stroma, is scarcely 

 discernible ; all that is left is a highly specialized protoplasm ; 

 and here the only change we know is that from reduced to oxy- 

 haemoglobin, and vice versa. Intermediate between the last two 

 stand such mechanical tissues as cartilage, bone, connective tis- 

 sues, and, we must add, nerve fibres and muscle. These, when 

 adult, consist chiefly either of comparatively inert intercellular 

 substance, or of what we may consider a special development 

 of a fibrillar cell-reticulum. And, aside from mere changes in 

 form, muscular contraction, reticular contraction as seen in 

 amoeba and ciliated epithelium, etc., and possibly the changes 

 in archoplastic spheres and filaments, where do we find changes 

 in the reticulum of cells .-' 



In running through the list of tissues, therefore, to ascertain 

 what changes connected with functional activity have been ob- 

 served in each, we shall watch for the following points : — 



1. Changes in nucleus. 



„ ^, . . , \ a. Granulation. 



2. Changes in protoplasm > 



) b. Reticulation. 

 I question the advisibility of further refinement at present. ^ 



^ It is immaterial to my present purpose, although it may not be to a future one, 

 whether we consider the structure of protoplasm to conform to any of the views 

 advanced since the " structureless slime " of Dujardin and Von Mohl. Protoplasm 

 must be something more than this. Lymph is constantly soaking through it, and 

 plus this are certainly granules of some sort and a fibrillar meshwork of some kind. 

 In this research I am not using sufficiently high powers, or sufficiently special methods, 

 to make it a matter of importance whether protoplasm is the zoogloea of special 

 bacteria of Altmann, or the foam of Butschli. I therefore adhere to the old familiar 

 view of Briicke, Arnold, and Max Schultze. 



With regard to the nucleus, the writer has often wished that he had applied 

 methods which would have enabled him to follow the substance, chromatin, a little 

 more closely. This might have been possible as it was, had there not been so many 

 different kinds of safranin in the market, with the exception of one sample, none of 

 which stained chromatin properly. This may be remedied in future, and the matter 

 does not concern us vitally at present 



