1 1 



blue, containing one part of the clye in 20,000 of physiological saline. It is then slit open 

 longitudinally and spread upon a slide with the serous coat uppermost. A glass cover is laid 

 upon it with slight pressure. A little thick gum at the angles will serve to keep it in place. 

 This preparation can be viewed even with an immersion lens. The plexus of nerves will be 

 distinctly seen. 



Subsequently, Ehrlich himself, followed by other workers, found that various 



FIG. 11. PORTRAIT OF PAUL EHRLICH. 



other dyes are taken into living cells and deposited in them. Instances will be 

 found in other parts of this book. Special structures have been found to be 

 stained by particular dyes, and valuable information obtained (see the book 

 by Goldmann, 1912). In the present state of knowledge of the physics and 

 chemistry of the cell it is impossible to make definite statements as to the 

 meaning of this specific staining of certain structures by particular dyes. Ehrlich 

 holds that the dyes have special affinities for certain " side-chains " of the 

 protoplasmic molecules ; but recent work has shown that many other conditions 

 also play a part, such as solubility, electric charge, diffusibility, and so forth. 



