CHEMISTRY OF THE CELL NUCLEUS 203 



employ mixtures of these to stain microscopic objects. If, for 

 instance, one applies a mixture of a basic dye (such as 

 methylene blue) and an acid dye (such as eosin) to a film of 

 blood, a selective action is exerted by the constituents of the 

 colourless corpuscles ; some parts will take up one stain, 

 others another, and one obtains not only a pretty preparation, 

 but, what is more important, facts which enable us to classify 

 the corpuscles. Parts which have an affinity for the acid stain 

 will be coloured red, and are called oxyphils or acidophile ; parts- 

 which have an affinity for the basic stain will become blue, 

 and are called basophilc ; in the case of the blood corpuscles, 

 granules with an affinity for methylene blue are comparatively 

 rare, although, as we have seen, the Nissl granules of nerve 

 cells are intensely basophile. Most of the granular contents 

 of the protoplasm of the white blood corpuscles or leucocytes 

 are either neutrophile or oxyphile. But in all cases, whether 

 we are dealing with blood, or nerve cells, or any other kind 

 of cells, the nucleus is always basophile. The chemical 

 explanation of this is not accepted by all observers ; still, it 

 is difficult to believe that the acidity of the nucleus (rich as 

 it is in nucleic acid) is entirely unconnected with its affinity 

 for basic substances. 



The methods of micro-chemistry are, after all, not so decisive 

 as those of macro-chemistry. It is an axiom with all practical 

 chemists that they can obtain better results and eliminate 

 errors of analysis when they work with large quantities of 

 material, and the investigation of the nucleus has proved no 

 exception to this rule. In order to obtain nuclei in abundance, 

 it is necessary first to take large quantities of cells, adopt 

 means to dissolve away the cell protoplasm, and to leave the 

 nuclei unaffected ; these can be collected and then the test- 

 tube and the flask come into requisition in the usual laboratory 

 processes. Luckily such methods have been found, and 

 accidental changes in the nuclei produced by the reagents 

 added to obtain them have been minimised though not yet 

 absolutely excluded. 



The earliest to attack the problem was Sir T. Lauder 

 Brunton, who as a young man spent some months working 

 in Kuhne's laboratory at Heidelberg. He obtained the nuclei, 

 of the red corpuscles of birds and snakes ; these were washed 

 free from serum by salt solution, then shaken with water and 



