PREPARATION, MOUNTING, AND COLLECTION OP OBJECTS. 191 



out such guidance cannot be attained. When the Microtome is employed 

 for this last purpose, the saw may be most conveniently worked vertically; 

 and this is readily done by detaching the instrument from the table, and 

 holding it down upon its clamp-side, which is so shaped as to afford a. 

 level support. 



186. In what is known as the Strasburg Microtome, invented by 

 Prof. Schiefferdecker, the substance to be cut is fixed in the cylinder by 

 binding-screws, while the circular cutting-bed, instead of being fixed on 

 the upper end of the cylinder, is made to screw upon it, so as to be raised 

 or lowered by turning it round. Thus, after a section has been taken, a 

 slight lowering of the cutting-bed, measured by the graduation of its 

 margin, prepares it for the cutting of the next. ' The simplicity of this. 



Hailes's Microtome. 



The two upper figures show the instrument (l) as seen from the side, (2) as seen in section : A, 

 outer cylinder, carrying upper flange c, on whose surface lie two strips of hard steel, 6, 6; this 

 flange is fixed to the bar o, which carries a clamp and screw for attaching the Microtome to a table ; 

 in the sec f 'onal figure (2) is seen the inner tube c, within which the substance to be cut is fixed 

 by the two binding screws, r, c, which work through a slot in the outer cylinder; to the bottom of 

 the inner tube is fixed a block D. through which works the micrometer-screw B, turned by the 

 milled-head e in the bracket F attached to the bottom of the outer cy under, and having a graduated 

 collar/. 



The two lower figures show the additional Saw-guide, seen from the side at 3, and from above 

 at 4 : 61, metal block with a screw to secure it on cutting-bed; ft 2 , 6 2 , steel guides. 



instrument, which is made to be held in one hand whilst the section is 

 cut with the other, is its great recommendation. 



187. Imbedding and Freezing Microtomes. For making thin sections 

 of soft tissues, however, preference is now generally given to Microtomes 

 in which the substance to be cut is so imbedded in some material that 

 fills the cylinder, that it does not need to be fixed by binding-screws, 

 being pushed upwards by the action of the micrometer-screw beneath 



1 " Quart. Journ. of Microsc. Science," Vol. xvii. (1877), p. 35. Another Micro- 

 tome, suggested by the preceding, is described by Mr. W. Teesdale in "Journ. of 

 Roy. Microsc. Soc.," Vol. iii. (1880), p. 1035. 



