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III. — On Cutting Sections of Animal Tissues for Microscopical 

 Examination. By Joseph Needham, F.B.M.S., &c, Demon- 

 strator of Histology at the London Hospital Medical College. 



(Read before the Medical Microscopical Society, April 18th, 1873.) 



Knowing the primary object of this Society to be the diffusion of 

 practical knowledge amongst its members, I shall endeavour to 

 further that object, this evening, by taking into consideration the 

 various methods of cutting sections for microscopical examination. 



It is not my intention to enter into the history of the subject, 

 for time will not permit ; we will, therefore, proceed at once to the 

 more interesting part, which will be practically demonstrated. 



We have three classes of tissues to deal with, each differing in 

 consistence. Bone may be taken as the type of the first or hard; 

 cartilage of the second or intermediate, and kidney of the third or 

 soft. 



I. Sections of hard structures, as bone, teeth, &c, are to be 

 made by a gradual wearing away of the tissues on two opposite 

 sides, corresponding in position, the planes of these sides being kept 

 parallel to each other till the required thinness is attained; this 

 may be accomplished in two ways, as follows : — 



1st Method. — Deprive a bone of the ligaments, muscles, and 

 tendons attached to it— in a way that will be presently described — 

 and dry it ; then firmly fix it in a vice, and divide it into thin plates 

 by means of a very fine bow-saw, the blade of which should be made 

 of watch-spring and held by screws : place a portion of bone so 

 obtained on a flat surface, and remove the first excess by means of a 

 file ; several files may be used for this, commencing with a coarser 

 and finishing with a finer. The section is to be now placed on a 

 good flat hone, and rubbed down on both sides to the required thin- 

 ness, being kept in contact with the stone by the pressure of the 

 finger or thumb, or fixed on a piece of cork. Although the section 

 is now thin enough, and sufficiently smooth for mounting in Canada 

 balsam, yet when viewed as a dry object, will be found to exhibit 



EXPLANATION OF FIGURES. 



Fig. 1. — Section of plano-concave razor. 

 „ 2. — Section of bi-concave „ 



„ 8. — Section of flat „ 



„ 4. — Upper surface and vertical section of Refrigerating Microtome, a, brass 

 plate, with hole in centre ; 6, tube fixed to ditto ; c, plug ; d, graduated 

 screw ; e, indicator ; /, oblong box to contain the freezing mixture ; 

 <j, tap to carry off water. 



Drawn to a scale of one-half. 



