STAINING. 157 



rather appear to be a diffuse coloration of the nuclear sub- 

 stance, which is a very different thing. 



I have myself made a considerable number of observations 

 on the subject of intra-vltam staining, and have come to the 

 same conclusion as GALEOTTI (Zeit. f. iris*. Mik., xi, 2, 1894, 

 p. 172), namely that the so-called " intra-vitam ' stains are 

 not true stains at all. The diffuse coloration above men- 

 tioned appears always, if the cell that shows it has remained 

 in a state of unimpaired vitality, to be due to simple absorp- 

 tion or imbibition of the colouring matter by the cell, not to 

 a molecular combination, of the colouring- matter with any of 

 the constituents of the cells. If a cell thus coloured be 

 transported into a medium free from the colouring matter it 

 will give up unchanged the colour it had imbibed, which 

 seems to be a sufficient proof that the colouring matter had 

 not entered into any molecular combination with the elements 

 of the cell, but was simply loosely held in a mechanical way 

 in the interstices of its substance. If, 011 the other hand, there 

 has been produced the above-mentioned coloration of certain 

 granules or other cell-contents, it is possible that this may 

 be a true stain in the sense of being such a combination as 

 is formed infixed material when stained. It may be so, but 

 it certainly is not always so, as may sometimes be proved 

 with the greatest ease by putting the cell into a colourless 

 medium and observing the supposed stain disappear. And 

 in cases in which this does not happen, in which, there- 

 fore, a more or less fast stain has been obtained, it is 

 invariably found that the stain is limited to cell-contents that 

 do not form an integral part of the living texture of the 

 cell ; the cell itself may be living, but they are not. These 

 granules or other cell-contents may be granules formed of 

 substances that have been absorbed by the cell from with- 

 outfood-granules ; or they may be katabolic products, con- 

 sisting of matter that is no longer alive and is destined to be 

 shortly expelled from the cell ; or they may be elements that 

 form indeed an integral part of the living texture of the cell 

 but have been injuriously affected by the colouring matter, 

 and for that or some other reason are in a state of diminished 

 vitality, they are parts of the cell that are being killed by 

 the colouring reagent or that have been totally killed by it, 

 whilst the rest survives ; in no case do they consist of matter 



