ZOOLOGY AND BOTANY, MICKOSCOPY. ETC. 981 



exudation of the liquid iu the smaller vessels takes place so rapidly 

 tliat the mass hardens very quickly in them. The larger the vessel 

 the more slowly, of course, do the exudation and consequently the 

 hardening take place. It sometimes happens that large vessels, like 

 the aorta, are not fully distended after the exudation of the liquid. 

 In this case some mass containing double the ordinary amount of 

 starch can be advantageously injected in two hours or longer after 

 the first injection. 



Dry Preparations. — Finally, if vessels injected with the starch 

 mass are dissected free, soaked a day or two in Wickersheimer's 

 preservative, and then dried, they retain their form, and to a great 

 degree their flexibility. 



Imbedding in Sticks of Paraffin.* — J. S. Kingsloy describes a 

 convenient method of imbedding. Small sticks of paraffin, fitting the 

 holder of the microtome, are cast in quantity in suitable paper moulds 

 and are laid aside until wanted. When it is desired to imbed an 

 object it is treated as for any paraffin imbedding. When thoroughly 

 impregnated with paraffin, a bit of wire is heated and with it a hole 

 is bored in one of the sticks of paraffin and the object is quickly 

 inserted. 



This method is especially adapted for cutting transverse sections 

 of elongated objects such as tadpoles, and furthermore it obviates all 

 danger of overheating the specimen. With objects of spherical shape, 

 of which sections ai'e desired in any particular plane, it affords no 

 especial advantage. 



" Microtoniy-"t— J. A. Ryder suggests the word "microtomy" 

 for the " new art " which has within a very recent period been de- 

 veloped, including both the processes preliminary to the actual cutting 

 of sections, and also those necessary for mounting. 



Gray's Ether Freezing Microtome. — The improvements in this 

 microtome, the design of the Rev. Metcalfe Gray, consist in the 

 holder for the knife, and iu the addition of guides, that the direction 

 of the cuts may be uniform, while steadiness is secured. 



All workers with tools know how important it is that they should 

 be held at the proj)er angle to the work, in order to secure the best 

 results, and the fault of many if not all section-cutters in which 

 plane-irons or chisels are used is that there aro no means whereby 

 this object may be attained, the results in consequence dei^eudiug 

 upon knowledge and skill, which many to whom sections would be 

 most valuable have no time to acquire. 



To meet this difficulty an iron duplex piano has been altered by 

 cutting away the coimecting bar in front of the end slot, so that the 

 iron is fixed firmly at the projier angle, and has the greater part of its 

 front surface clear, up which the sections as they are cut may slide 

 without obstruction. The cutting edge of the iron is ground level on 

 a piece of plate glass with emery powder, and afterwards sharpened. 



♦ Science III conl, ii. (1884) p. 175. 



t Aiuer. Mull. Micr. Jouiii., v. (,l«8l) pp. 190-1. 



