212 



SCIENCE 



[Vol. LV, No. 1417 



A SIMPLE METHOD OF DEALING WITH 

 ELECTRIFIED MICROSECTIONS 



Electeifioation of the sections is a frequent 

 cause of trouble in microtomy. Tlie sections 

 when cut fly back into the paraffin block when 

 the block rises for the nest cut, or, if a short 

 ribbon has already been cut, this flies to the 

 knife, twists and curls, or "bunches up" on 

 the knife in such a way that it is an exceedingly 

 wearisome task to seriate the sections, and re- 

 quires almost infinite care and patience. The 

 causes of electrification may be various. It is 

 owing either to atmospheric conditions or to 

 faulty methods of infiltrating or blocking. The 

 use of a metal drum on which the sections may 

 be wound as cut, reduces somewhat, as is well 

 known, the difficulty experienced because of the 

 electrification of the sections. The suggestion 

 of Guj'er (p. 47 of his revised ed. of Animal 

 Uicrology 1917) to postpone cutting till a more 

 favorable time is not very satisfactory to one 

 who is compelled, because of press of time, to 

 cut continuously. The following simple device 

 I have used with electrified sections and have 

 found very satisfactory. The labor of mount- 

 ing such sections, by its use, has been very much 

 reduced, and I believe it will be quite generally 

 serviceable. 



Fig. 1 



screwed flat against the section-knife by means 

 of the usual knife-holding screws of the car- 

 riage. (Fig. 2). A long narrow strip of thin, 

 tough paper is passed up between the celluloid 

 blade and the microtome knife, until about 3 

 cm. of it protrudes above. After the paraffin 

 block has beeu properly trimmed and adjusted 

 to the knife, the sections are cut, and as each 

 one is cut, it is attracted and held by the paper- 

 strip which is pulled along with the fingers so 

 as to produce a series. (Pig. 2). When the 

 strip is nearly filled with sections, it is taken 

 and fastened to the table or board with thumb- 

 tacks, to keep it from curling, and another strip 

 substituted. 



By means of this extremely simple device, 

 the writer has found it possible to cut with ex- 

 cellent seriation material which othei-wise, ow- 

 ing to electrification, would have been impos- 

 sible. 



S. W. Geiser 

 Zoological Laboratory, 



Tee Johns Hopkins University 



Figures 1 and 2 show the whole device, which 

 is adapted to any of the common types of 

 rotary microtomes for the cutting of serial sec- 

 tions. It consists of a thin blade of celluloid 

 (one of the 6-inch rulers furnished by the bio- 

 logical supply-houses does very well). This is 



THE AMERICAN CHEMICAL 

 SOCIETY 



{Continued) 

 Division op Industrial and Engineering 

 Chemistry 

 H. D. Batchelor, Chairman 

 H. E. Howe, Secretary 

 SYMPOsruM on Filtration 

 D. K. Sperry, CJiairman 

 Filter cloth and its relation to filtration: Alvin 

 Allen Campbell. Filter clotli is a very im- 

 portant consideration. Principal kinds are made 

 of cotton, wool, jute, liemp, nickel and monel 

 metal. Cotton duck the most used, but being 

 replaced by materials of longer life thougli not 

 necessarily better filterers. Solids really are the 

 filter medium, the cloth is merely the retaining 

 wall. The combination of strength, fineness and 

 rapidity is what is wanted. Life of cloths de- 

 pends on chemical action tending to destroy its 

 use. Considers monel metal the best cloth mate- 

 rial in most cases. Gives interesting list of vari- 

 ous acids and salts and whether or not monel 

 metal is recommended. Warns against electro- 

 lytic action on monel cloths, citing potassium 

 permanganate as a ease in point. Gives opinion 



