50 THE AMERICAN MONTHLY [Feb 



seen in the field of view ju8t surrounding the ohject. In 

 some cases it is better to use a triangular rather tliau a 

 circular loop, so as to minimize the risk of mistaking cir- 

 cular effects. 



Fluid Mounts. — To preserve for an indefinite period 

 such fluid mounts as fish embryos, ova, and the like, it is 

 necessary to use a cement having exceptional strength 

 and fluid-resisting properties. The following cement is 

 admirably adapted for this purpose. Take two parts of 

 carbonate of lead, two parts of red oxide of lead, and 

 three parts of litharge. Grind these very finely, mix them 

 dry and keep in a wide-mouthed bottle. When required 

 for use a little of the powder should be mixed with old 

 gold size on a watch glass. It is necessary that there 

 should be no trace of grit or unground matter in the mix- 

 ture. A cell made with this cement may be filed oflf the 

 glass slip without the cell breaking away. 



Tumors. — In a paper recently read before the Manches- 

 ter Microscopical Society, Mr. J. V. Wolstenholme, f. r. 

 M. s., gives details of the methods that were employed in 

 his investigations on the micrococci (Botriomycetes), which 

 produce the tumors in domesticated animals. He removed 

 from the groin of a horse a pear-shaped tumor, the mass 

 of which was dense, firm, and resistant, and of a pale 

 pink color. In the centre was an abscess cavity, two and 

 a half by one and a half inches, which communicated by 

 narrow channels with a large sore or ulcer at the base of 

 the tumor. For microscopical examination, portions of 

 this tumor were hardened in (a) Muller's fluid, (b) picric 

 acid, (c) alcohol, after which they were easily cut with the 

 freezing microtome, and stained readily. In some cases 

 it was found to be an advantage to embed the portion of 

 tissue in celloidin before cutting. The stains used were 

 (a) picro-carmine, (b) hsematin followed by picro-carmiue, 

 (c) haBmatin,and then rubin and orange combined, (d) the 

 Plantz method. Of these, the hsematin with rubin and 



