SOME REMARKS ON CLARIFICATION, ETC. 207 



refractive power is superior to that of chloral hydrate, without, 

 however, approaching too closely that of cellulose. It is, therefore, 

 for both reasons, more serviceable as a clarifier than chloral 

 hydrate. 



As far as its chemical clarification is concerned the action in 

 swelling the fecula is very prompt. No starch grains were percep- 

 tible in sections of ginger after they had laid in the solution about 

 two hours. The colouring of the cell walls is also less changed by 

 salicylate than chloral hydrate. 



The latter also gradually causes the cell walls to swell, and, in 

 the case of soft structures, they are sometimes rendered partially 

 imperceptible. 



In using salicylate I have not discovered this defect; it appears, 

 on the contrary, to have a hardening effect on soft tissues. 



If, as an instance, several thick sections of ginger-root, after 

 having lain about twenty-four hours in saHcylate, and the super- 

 fluous liquid carefully removed with filter paper, be mounted in 

 glycerine and examined, the cell walls will be found to be but 

 little swollen, and their colour, especially that of the cork cells, 

 well preserved. 



All the thin strata appear sharply outlined. 



In balsam mounts the details become even more clear and 

 beautiful. 



In objects which have been treated with chloral hydrate the 

 cell walls will be found more swollen, their colour fainter, their 

 outlines less clearly defined, and the structural details, although in 

 general discernible, somewhat obliterated. 



Chloral hydrate is, consequently, only serviceable in examining 

 thick objects, and when these are to be decoloured as much as 

 possible. Dyes containing tannin are more influenced by chloral 

 hydrate than by salicylate. The best way to eliminate them is by 

 means of alkaline solutions and afterwards, when necessary, with 

 Javelle water. 



Fecula, when swollen in chloral hydrate, forms a transparent 

 jelly, which becomes considerably turbid when a small quantity of 

 water or glycerine is added ; a turbidity which increases and forms 

 a thick deposit if this supply is increased. 



The jelly produced by fecula swollen in salicylate is much more 



