1S98.] of ''Connecting Th-is" in the Cell Wall. 511 



doubt the phenomenon is partly one of simple diffusion, and 

 results from the circumstance that diffusion into the protoplasm 

 is easier than into the refractory and markedly mucilaginous cell 

 wall. But in addition to this simple diffusion there also appears 

 to be a definite selective affinity between the Iodine and the 

 dead protoplasm, which stated more philosophically is in reality a 

 chemical affinity, as is also in a smaller degree diffusion itself. 



But be this as it may, the extraordinary rapidity with which 

 mere traces of Iodine are absorbed by the protoplasm and the 

 threads is almost beyond belief. 



The precise manner in which the Iodine travels from cell to 

 cell is not quite clear, but in certain instances I am led to believe 

 that it is via the threads rather than via the walls. 



Not less important than the relations between the protoplasm 

 and its mordant are the relations between the mordant and its 

 dye, but all that one need say on the present occasion is that 

 Iodine and many of the Aniline violets have an intense affinity 

 the one for the other, and that even in the most dilute solutions 

 where only traces are present the characteristic precipitate which 

 plays so important a part in the Iodine- Acid- Violet method is at 

 once formed. 



A second and almost equally important factor in the success of 

 the method is the part played by the sulphuric acid as the solvent 

 of the Aniline violets; and in this connection two joints especially 

 deserve notice, viz. (1) that the dye when first dissolved in the acid 

 exists in a very perfect state of solution, and (2) that upon solution 

 the tinctorial properties of the dye become profoundly modified. 



As to the first point it will be found that watery solutions 

 of the Violets penetrate into tissues with some difficulty, but that 

 alcoholic solutions, and especially solutions in acids, are much more 

 readily diffusible. 



The second point is however much the more important, and it 

 is this ; that Gentian violet or Pyoktanin when dissolved in 

 sulphuric acid stains the protoplasmic structures only and ceases 

 to colour the cell wall. That this is so may be easily demonstrated 

 by the following experiments, A and B. 



A. (1) Sections of normal tissue having been treated with an 

 aqueous solution of the Violet — the cell wall and protoplasm are 

 both deeply stained. 



(2) Sections of tissue having been swollen with sulphuric 

 acid and washed and treated with an aqueous solution of the 

 Violet — the results are practically the same as before. 



B. (1) Sections of normal tissue treated with a "5 °/ solution 

 \ of the Violet in 5 °/ o solution of Sulphuric acid — the protoplasm 



is stained but the cell wall hardly at all. 



