STAINING 135 



The nucleus itself seems to be very resistant to dyes while alive, 

 and it has been stated that the appearance of stain in it is a sure 

 indication of death. Bolles Lee made a large number of 

 observations and came to the conclusion that most of the " intra- 

 vitam " stains are either due to mere diffusion through the liquid 

 protoplasm or that the stained constituents were not really living, 

 being food particles or products of cell activity. 



At the same time, many of the methods which come under this 

 heading are of much value. Methylen blue may be injected into 

 the living animal and frequently gives very successful staining of 

 nervous structures, owing to the fact of its being conveyed into 

 intimate contact with the cells by means of the blood vessels. 



The various methods of j^reserving the stain in the structures 

 to which it was localised during life obviously depend on the 

 adequacy of the means used to fix and maintain these structures 

 and to retain the properties owing to which the stain was taken 

 up. This is by no means a simple matter. Mott describes in 

 living nerve cells a number of minute particles which stain on 

 the outside with methylen blue. In fixed cells, as is well known, 

 these particles aggregate together to form the " Nissl granules." 

 MiCHAELis found similar granules in liver cells. As the cells die, 

 the stain leaves the granules and passes into the nucleus. 



The behaviour of the living nucleus to methyl green has given 

 rise to some discussion. It appears that no uni-cellular organism 

 in which the nucleus was so stained has been observed to move, 

 whereas the chlorophyll grains may take up the stain while the 

 cell is normally motile. 



The question as to whether the cell elements which stain during 

 life are to be described as living or not is scarcely putting the 

 problem from the right point of view. If a dye obtains contact 

 with the interfaces between constituents of a cell, it will in all 

 probability be deposited there to a degree depending on the various 

 properties of the interface described previously. This may occur 

 independently of the fact as to whether one or both of the phases 

 is living. 



The details of the various methods used for intra-vitam staining 

 and the fixation of the results are described in other parts of this 

 book. The reader may be referred to the work of Goldman 

 {Unters. ueher die Sekretion des Organismus im Lichte der " vitalen 

 Fdrbung,'" Laupp ; Tiibingen, 1912) for certain aspects of the 

 problem. A splendid summary is given by Cappell, (J. Path, 

 and Bad., vol. 32, 1929). 



244. Fixed Tissues. The majority of staining methods are 

 undertaken on tissues that have been fixed and hardened by 

 reagents. It is sufficient to mention here that some of these 

 reagents merely serve to coagulate or precipitate the constituents 

 of cells without marked changes in their chemical nature, although 



