2636 Journal of Applied Microscopy 



■« 



GENERAL LABORATORY TECHNIQUE. 



RAYMOND PEARL, University of Michigan. 



Books and Papers for Review should be Sent to Raymond Pearl, Zoological Laboratory, 

 University of Michigan, Ann Arbor, Mich. 



A Method of Obtaining Uniplanar Sec= One of the chief objections to that 

 tions with the Ordinary Rocking otherwise very satisfactory piece of 

 Microtome. , , , '^ , • , 



laboratory apparatus, the Cambridge 



Rocking Microtome of the old pattern, has always been that the sections cut 

 were not uniplanar, but were instead segments of a cylinder. While this defect 

 is not serious when the area of the face of the block is small, it becomes an impor- 

 tant matter when the area is large. W. S. Handley (Jour. Anat. Physiol., Vol. 

 XXXVI, pp. 290-292, 1903) has described a method of obviating this defect 

 which will be found useful by users of the type of microtome mentioned. His 

 method essentially consists in embedding the slice of tissue to be cut on a cylindri- 

 cal surface, corresponding to the curve described by the rocking arm of the 

 microtome. "A squared block of paraffin, sufficiently large to contain the piece 

 of tissue to be cut, is fixed on the rocking arm, with its center truly in the axis 

 of the arm, with its upper edge horizontal, and wiih its free surface forming a 

 plane at right angles to the axis of the arm. These points can be judged with 

 sufficient accuracy by the eye. This pattern block is now cut in the ordinary 

 way until its cut surface has acquired the convex cylindrical form, and complete 

 sections of it are being cut by the razor. It is now dismounted, covered with 

 thin tinfoil, and surrounded by a projecting rim of stamp-paper. A mould with 

 a convex cylindrical tioor is thus produced, and into this plaster of paris is 

 poured as it stands on a level surface. When the plaster has set, it forms a 

 square or oblong block with one concave cylindrical surface. Tinfoil is swagged 

 down upon this surface, and the edges of the block surrounded by a rim of 

 stamp-paper. The embedding mould is now ready. The slice of tissue is very 

 thin, say not more than one-eighth inch thick, for two reasons. First, since the 

 sections are uniplanar, very much thinner pieces may he used, which is one great 

 advantage of this method. Secondly, unless the piece of tissue is thin, it does 

 not adapt itself properly to the concave floor of the embedding mould. During 

 the process of embedding it is necessary to hold down the slice of tissue with 

 hot needles until the paraffin has set sufficiently to hold it in its curved position 

 on the floor of the mould. While the paraffin is cooling, the mould must of 

 course stand on a horizontal surface. The paraffin block thus obtained must be 

 detached from the mould and fixed truly on the rocking-arm, in a position exactly 

 corresponding to that of the pattern-block from which the mould was made. 

 The razor will at once commence to cut complete sections of the curved surface 

 of the block." 



Handley states that by this method he has been able to obtain uniplanar 

 sections from blocks Ij/; inches in diameter without difficulty. R. p. 



Ink for Glass '^^^ Pharmaceutical Era (September 



24, 1903) gives the following method 

 of making ink for writing on glass: Dissolve 20 parts resin in 150 parts of 

 alcohol and add to this solution, drop by drop, and under continuous stirring, a 

 solution of 35 parts borax in 250 parts water. Finally dissolve 1 part methylene 

 blue in the mixture. r. p. 



