ZOOLOGY AND BOTANY^, MICROSCOPY, ETC. 449 



Deecke's Microtome— Cutting and Mounting Sections through, 

 the Entire Human Brain.* — Dr. Deecke's microtome used for this 

 purpose is a heavy brass cylinder of the Eauvier form, and is 9 in. in 

 diameter and 14 in. high. The piston can be raised by the screw 

 with great accuracy, the 1200th, the 600th, the dOOth, &c., part of an 

 inch, thus by the aid of an index graduating the thickness of the 

 sections. As the sections must be cut under alcohol, the microtome 

 is inserted in a basin of copper, 18 in. by 30 in. by 4 in., placed on a 

 suitable table frame. The brain to be cut is placed upon the piston 

 and held in situ by several pieces of soft cork. It is then imbedded 

 in a cast of paraffin, olive oil, and tallow -which, after it has become 

 hard, is held in position by a number of small curved rods attached 

 to, and projecting upwards from the piston to the height of about an 

 inch. Before cutting, and as it proceeds, the cast is carefully 

 removed from around the specimen to the depth of about i in. (which 

 is easily done by the use of a good sized carpenter's chisel), so that 

 the knife never comes in contact with the cast. 



The knife has a blade to which upright handles can be fastened 

 by screws; the cutting edge is 16 in. in length, the blade IJ in. 

 broad, and l-4th in. thick at the back. To this a steel rod is attached 

 by screws, which project 1-1 6th in. downwards, so that the knife, 

 when placed upon the microtome, rests only upon its edge and the 

 rod, leaving a free space between the lower surface of the blade and 

 the upper of the cylinder, by which arrangement the alcohol is 

 allowed access to this space, thus preventing almost entirely adhesion 

 between the two surfaces. The general form of the knife is that of a 

 chisel. When the instruments are made accurately their construction 

 enables the operator to move the knife forward with a slight sawing 

 motion or, better, in short cuts, while the weight of the knife itself 

 fully suffices to prevent any deviation from its course, and renders it 

 unnecessary to use any amount of pressure. This manner of cutting 

 of course requires practice and a light, firm, and steady movement of 

 the hands. It becomes necessary, after each step forward, to draw 

 the knife a little back, in order to be sure of not losing a particle of 

 the section. The sections will, it is true, show slight traces from 

 this way of cutting ; this does not, however, interfere in the least 

 with the examination of the specimens or with their beauty ; in fact, 

 they are so slight that they can scarcely be recognized after the 

 sections are mounted. Moreover, the longer the instruments are in 

 use the more perfect they become when carefully kept and handled. 



This method oiFers great advantages over that by one sweep, in 

 that the sections come out much more uniform in thickness and more 

 perfect in all their parts, and the loss in a series of successive sections 

 of from four hundred to five hundred to the inch — for example through 

 the entire cerebrum of man — by an experienced operator, may not 

 amount to more than 2 or 3 per cent. Furthermore, there is no 

 necessity, as in the German method of cutting in one sweep (Gud- 

 den's), to remove, before hardening an organ like the brain, the 



* Description supplied by Dr. Dcecke (slightly condensed). See also Proc. 

 Amer. Soc. Micr., 5th Ann. Meeting, 1882, pp. 275-7, 279-80. 



Ser. 2.— Vol. III. 2 G 



