PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS. 193 



in its handle; whilst on the .latter there slides an Object-carrier, consist- 

 ing of a clamp, whose opening is controlled by a binding-screw, for hold- 

 ing the block of paraffine in which the substance to be cut is imbedded. 

 From this description, it will be obvious that when the carrier that bears 

 the knife (as seen at A) is slid from one end of its shelf to the other, the 

 knife always remains on the same level; but that when the Object-carrier 

 is similarly slid (from right to left in Fig. B), it gradually rises, always 

 keeping at the same height in relation to the inclined edge of the vertical 

 plate. This edge being graduated, and a 'vernier' being engraved on 

 the carriage, the progressive elevation of the surface from which the 

 section is to be taken can be measured with the most minute exactness; 

 as the substitution of the inclined plane for the screw altogether does 

 away with the * lost time ' from which the action of the latter is seldom 

 entirely free. The manner in which the knife is attached to its carriage, 

 enables it to be so fixed as to give any proportion that may be desired 

 between the sliding and the pressing cut. The simple model here 

 described is extensively used on the Continent; and the Author can 

 indorse its reputation from large personal experience. Certain modifica- 

 tions have been recently made in it, however which must not be passed 

 without notice. One of these re- 

 lates to the mode in which the FIB. 

 block of paraffine is held in its car- 

 rier, so that the position of the 

 body imbedded in it may be varied, 

 without taking the block out of 

 the clamp. The screw a (Fig. 

 136), working through the fixed 

 piece #, brings the movable piece c. 

 (which is guided by two pins that 

 work through b) against the fixed 

 piece d, and thus secures the body 

 to be cut. The clamp is connected 

 by means of the bent arm e with the 

 block /, the upper surface of 



which is rounded ; and On this it Can Improved Object Carrier for the Rivet-Leiser 



be moved in a plane parallel to the 



middle plate of the instrument, so as to take a position more or less 

 oblique in which it may be fixed by the binding-screw g. The block / 

 again is connected with the fixed block h, by a pivot passing through the 

 latter; and on this it may be rotated in a plane at right angles to the 

 middle plate, being fixed in any position by the binding-screw i. By 

 the combination of these two movements, the object can be placed (and 

 then fixed) in such a position that the sectional plane shall traverse it 

 in any desired direction. The knife-carrier is also furnished with screws 

 that enable the inclination of the blade to be regulated with great pre- 

 cision. And, if desired, the object-carrier may be advanced up its 

 incline by a screw traversing the entire length of the instrument, instead 

 of by hand; an addition, however, which seems to the Author quite 

 unnecessary, and certainly not worth its cost. ' This Microtome can be 

 made in hard wood at a lower cost than in metal, and with very little 

 sacrifice (if any) of efficiency; and it has lately been recommended that 

 the body of the instrument should be divided longitudinally, and its two 



1 " Journ. of Roy. Microsc. Soc.," Vol. ii. (1880), p. 334. 

 13 



