186 Blue and Violet Stainings for Vegetable Tissues. 



At the operator's pleasure the chlorinated leaves may be soaked 

 in pure water for an hour, and afterwards in a 3 per cent, aqueous 

 solution of alum, in preparation for the logivood staining. 



If the aniline blue dye be chosen, let the acidulated leaves be 

 immersed in the blue fluid, and soaked for twenty or thirty 

 minutes. Upon being withdrawn their colour will be found to be 

 very intense, but washing in 90 per cent, alcohol for half a minute 

 will remove superfluous aniline, a,nd a final bath in absolute alcohol 

 will in a few minutes prepare the object for being soaked in oil 

 of cloves. With a bent platinum spatula the transparent prepara- 

 tions must be laid upon a slide, receive a liberal quantity of a 

 solution of old balsam in chloroform poured upon it, and be covered 

 with thin glass, on which a small weight is to be placed. 



In the course of a month or two the excess of balsam may be 

 cleaned ofi", but the slide should bear a provisional label before the 

 specimen is mounted. 



The hsematoxylin staining is, perhaps, rather more successful 

 than the anihne, and its violet tinge is very beautiful indeed. Let the 

 transparent leaves or sections be transferred from the alum solution, 

 after a short residence, to Arnold's fluid undiluted. At the end of 

 five minutes remove one object and wash it in the alum solution ; 

 if not decidedly or sufficiently tinted return to the fluid and examine 

 it again at the end of another five minutes ; and when, finally, the 

 whole of the object shall have been evenly and distinctly coloured, 

 it must be dropped into the alum solution for a minute or two, and 

 then into 75 per cent, alcohol, in which the former dull red colour 

 will change to a lovely violet. In many cases the fluid, diluted 

 with 25 per cent, alcohol, will make a better staining, but, of course, 

 the object must have a longer exposure. 



For mounting immerse in absolute alcohol, then in oil of cloves, 

 and finally embalm in the chloriform solution of old Canada balsam. 



If the foregoing directions be strictly followed there will be no 

 difficulty with the logwood stainings ; but to secure good aniline 

 preparations all the steps of the process must be done completely 

 but with all possible dispatch, therein lies a secret of success. 



It is, perhaps, somewhat out of place in this paper to speak of 

 stainings of animal tissues ; but I beg to say that my results have 

 not, hitherto, been very satisfactory as regards aniline colours; 

 while, on the contrary, carmine has always succeeded perfectly, 

 and Arnold's fluid most beautifully, with sections of the nervous 

 centres. 



