INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 695 



haste. Then quickly place it iu clean alcohol, and brush lightly with 

 a camel's-hair brush. This immersion in clean alcohol seems to check 

 the operation of the blue instantly. It should then be examined under 

 a 1-inch objective to determine whether the exact point where the 

 blue and the red remain distinct has been reached. If the blue has 

 not occupied all the softer cells, another section should be taken and 

 put through the same process, counting twelve, and so on, until the 

 proper point is reached ; or, on the other hand, decreasing the count 

 if the blue has infringed upon the red in the more dense tissue. Having 

 thus determined the count for the sections of that particular material, 

 the remainder of the sections are passed through tlie blue into the 

 alcohol, merely counting off the immersion of each section. Then 

 place the sections for a few moments in absolute alcohol, which seems 

 to fix the colours, then through oil of cloves into benzole, and moiint 

 in dammar and benzole. It is sometimes advisable, with delicate tissues, 

 to merely rinse off the blue in 95 per cent, alcohol, and fix the colours 

 at once in absolute alcohol, but every operator will learn the minor 

 details for himself in the manipulation. 



Of course, with the " rule of thumb " method of counting off the 

 time slight variations will occur which will mar the beauty of the 

 finished product ; besides which minute differences in the thickness of 

 the section will affect the result, and even a distance of a quarter of 

 an inch iu the same stem will make a difference in the density of the 

 tissue, which will be obvious in the sharpness of the colours under the 

 objective, so that the operator should not be disappointed if out of a 

 dozen slides only four should be worth preserving. The others can 

 go into the borax-pot to be cleaned for another operation. The beauty 

 of those which do pass inspection will amply repay for the labour on the 

 spoiled ones. 



Tlie writer says that he has perhaps been needlessly minute in the 

 description of the process he has employed, but he has been so often 

 hampered by the lack of minuteness in descriptions of processes by 

 others, vvliich he has been endeavouring to carry out, that he deems it 

 better to err upon the safe side, even at the risk of being considered 

 dry or prosy. 



A no*e is added as to the uso of cosin. He was attracted to it by 

 its exquisite purity of colour under transmitted light, and its perfect 

 transparency. Sections preserved iu its solution were found always to 

 retain their transpai'eney, and did ncjt become clogged or tliiek with 

 colour, so that when taken out after months of innnersion the most 

 dense cells were no deej)er in colour than the solution itself. So far 

 as regards its hold upon the tissues, it is as strong as roseine, or any 

 of the heavier colours. He cannot testify as to its permanence, but 

 has some slides that were prepared over a year ago, and appear to bo 

 as bright and pure as when they were mounted. Contrary to tho 

 experience of some otliers, he has not found that tlie benz«do has any 

 bleacliing effect, and it has b^en used with dammar in preference to the 

 usual balsam. Slides prepared with dammur, however, should have a 

 thick ring of vaiiiish run around them, as the danim.ir is brittle, and 

 sliould not 1)(; trusted ub^nt,' to Jk^M tiic covering glass. 



