836 SUMMARY OF CURRENT RESEARCHES RELATING TO 



that the paper separates readily from tbe inclosed paraffin, and on 

 removing the bottom of the box in the same way the result is a solid 

 cylindrical block of paraffin, with the object to bo cut lying horizontally 

 close to the smooth lower face, so that the sectioning is easily regulated. 



Schonland recommends paraffin with a melting-point of about 45° C, 

 but the author found this much too soft to cut well, and prefers (as Moll 

 recommends) a harder sort, melting at about 50° C. Schonland again says 

 that a temperature above 50° C. is to be avoided, but in no case has the 

 author found that a temperature of 50°-55° C. was in the least degree 

 hurtful. 



For sectioning the rocking microtome used by Schonland was cm- 

 ployed, and found in every way satisfactory. 



Moll describes fully the fixing processes, but the author's experience 

 has been that it is not desirable to hasten the staining process. Safranin 

 was mainly used, and the best results were had by allowing the sections 

 to remain for about twenty-four hours in a very dilute watery solution. 

 At the end of this time they should be deeply stained. The slide is 

 then plunged in absolute alcohol until the excess of the colour is re- 

 moved, and when this is accomplished, and most of the alcohol has 

 been removed from the slide with a cloth or blotting-paper, taking 

 care of course not to touch the sections, a few drops of xylol are applied, 

 and allowed to remain until the sections look perfectly transparent, 

 when a drop of Canada balsam dissolved in xylol or chloroform may be 

 applied, and a cover-glass put over the preparation, which is now 

 complete. 



The employment of soft paraffin in order to make the sections adhere, 

 as described by Schonland, is quite unnecessary, as the sections adhere 

 perfectly without this ; indeed, it is much easier to get a good ribbon of 

 sections without the soft paraffin than with it, owing to the difficulty of 

 perfectly removing the surplus soft paraffin. 



Further Notes on Celloidin Technique.*— Dr. S. Apathy communi- 

 cates some further instructions for manipulating celloidin by way of 

 supplement to his previous paper.f 



(1) How to keep celloidin blocks. — If cork be used for sticking 

 the celloidin blocks on, it must first be saturated with soft paraffin in 

 order that the 70-80 per cent, spirit in which the object is to be pre- 

 served may not be spoilt by the tannic acid. But as celloidin will not 

 adhere to paraffin, the latter must be shaved off from one end, and then 

 this end, together with the celloidin block which has been stuck on, is 

 plunged for a second in some paraffin heated above its boiling point. In 

 this way a block of celloidin can be kept even without spirit without any 

 danger of its becoming dry. Sectioning must, of course, be done with a 

 dry knife. The thin casing of paraffin, even if it does not fall off of itself, 

 can be dissolved at once in bergamot oil, and offers no difficulty. If it 

 be desired to discontinue making sections, it is only necessary to cover 

 the exposed surface with a drop of paraffin. 



(2) Writing on celloidin. — Mark the bottom of the paper case in which 

 the object is to be imbedded wdth a lead pencil. Then, when the paper 

 case is stripped off from the block consolidated in 70-80 per cent, spirit, 

 the writing will be found transferred to the celloidin, and in order to 



• Zeitschr. f. Wiss. Mikr., v. (1888) pp. 45-9. 

 t See this Journal, wite, p. 670. 



