346 J. B. SCRIVEN ON PREPARATION OF SERIAL SECTIONS OF INSECTS, 



width by means of warm water,* as well as how to combine this 

 process with the use of Mayer's albumen and glycerine ; and 

 I find that sections of the fly can thus be very successfully 

 dealt with. 



A still greater improvement on the old methods, however, as 

 he further shows, is not only to stretch, but also to fix the sections 

 by means of warm water on a clean slide, without any adhesive 

 material. This also is applicable to the fly ; in fact, it is so much 

 better than Mayer's plan, that I think the latter may be discarded 

 altogether ; for the adhesion is much stronger on the clean side, 

 if the proceeding be conducted with sufficient care, always under- 

 standing that the sections are good, i.e., not torn or injured, as by 

 cutting with an insufiiciently sharp knife. 



To carry out the process successfully, it is necessary to be very 

 particular about the cleanliness of the slides, as Professor Lee 

 points out. Nevertheless I have not found it worth while to 

 follow him to the letter, and have never rejected a slide because 

 a line of water, or the breath, would not lie evenly upon it. Few 

 slides, it appears to me, come up to this ideal condition. The 

 temperature of the water used ought not to exceed 17° C. below 

 the melting point of the ribbon laid upon it : anything above this 

 is dangerous to its integrity. I cover the whole slide with cold 

 \vater, which is much easier than making a line of water, as 

 Professor Lee recommends. I then lay the piece of ribbon upon 

 it, or two pieces side by side, and put the slide on the top of the 

 water oven under a glass shade, not completely preventing com- 

 munication with the air of the room. There I leave it in the 

 horizontal position,t and do not touch it (except it be to keep the 

 ribbon in place with a camel-hair brush) till the water has 

 evaporated and the whole thing is dry, which occupies about 

 2 2 hours. Any attempt to remove superfluous water with a 

 brush, or to drain it away, as by setting the slide on end, seems to 

 me to diminish the strength of the adhesion. Professor Lee says 

 that tap-water is better than distilled : it leaves a little deposit 

 of chalk about the edges of the ribbon, (not under the sections), 

 which can be removed at a later period under water, partly with 



* " Microtomists' Vade Mecum," 5th edition, pp. 113 and MO sqq. See 

 also Carpenter's " The Microscope and its Eevelations," 8th edition, by the 

 Rev. Dr. Dallinger, pp. 501, 502. 



f Much trouble may be saved by using a spirit level. 



