ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 531 



Preparing Sections for Examination with the highest Powers.* 

 — Mr. J. W. Giflford thinks there is no more successful plan for de- 

 monstrating minute structure than Beale's process of preparing and 

 staining tissues in glycerin and then teasing them out with needles, 

 followed by the judicious application of heat and pressure, and finally 

 mounting in pure glycerin. The method, however, prevents the use 

 of the freezing microtome as glycerin freezes at so low a temperature, 

 and it therefore occurred to him whether the substitution of a colloid, 

 such as gum, for the glycerin at one stage of the process might not 

 act as well as glycerin in preventing change. 



The fresh material cut into small pieces should be placed in 

 Beale's glycerin-carmine until the bioplasm is stained (10 to 15 hours), 

 or better, inject the whole body or part with the stronger glycerin- 

 carmine, and allow it to remain until stained ; it should then be cut 

 into pieces. After this place it in 2 parts glycerin to 1 water for 24 

 hours, followed by pure glycerin saturated with picric acid for 48 

 hours. The pieces are then taken out of the glycerin and (of course 

 without washing) placed in a thick solution of gum acacia, also satu- 

 rated with picric acid, for 48 hours. The small quantity of glycerin 

 which adheres to them when placed in the gum and picric acid does 

 not much retard fi-eezing, and sections may easily be cut. 



As soon as the sections are cut they are placed in a mixture of 5 

 drops of acetic acid to 1 oz. of glycerin, and after remaining in this 

 for several days or a week will have swelled out to their original size 

 if shrunk at first by the glycerin, and may then be mounted in glycerin 

 with a trace of acid in the usual way. 



Osmic Acid and Merkel's Fluid for Pelagic Fish-eggs, &c.t — Dr, 

 C. 0. Whitman proceeds by placing the eggs with a little sea-water in 

 a watch-glass ; then by the aid of a pipette a quantity of osmic acid 

 (1/2 per cent.) about equal in volume to that of the sea-water is added. 

 At the end of from five to ten minutes the eggs are washed quickly 

 in water and transferred to a chrome-platinum solution, difiering from 

 Merkel's mixture in having a 1 per cent, solution of chromic acid. In 

 this they remain from one to three days. By this treatment the 

 blastoderm may be easily freed from the yolk and then having been 

 thoroughly washed in water for some hours, the preparation is passed 

 through the usual grades of alcohol, stained and sectioned or mounted 

 in toto. The platinum chloride not only completes the work of hard- 

 ening, but at the same time removes much of the brown or black 

 colour imparted by the osmic acid. By this method a very marked 

 differentiation is generally obtained as early as the 16-cell stage. In 

 later stages of cleavage the distinction between central and peripheral 

 cells becomes still stronger, so that it becomes possible to trace the 

 entire history of the origin of the so-called parablast. 



For the eggs of Clepsine Merkel's fluid is used, of its Ordinary 

 strength, for one or two hours only. Here the differential effects 

 extend not only to the different germ-layers, but also to cell-groups 



* Scientif. Enquirer, i. (1886) pp. 25-7. t Amer. Natural., xx. (1886) p. 200-3. 



