472 PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS 



allows the position of the imbedded object to be adjusted, so that at 

 the end of the forward stroke it is only just past the edge of the 

 razor. This is an important adjustment, as it causes the razor to 

 commence the cut when the object is travelling slowly, and produces 

 the most favourable conditions for the sections to adhere to each 

 other. 



The following are perhaps the most prominent advantages of this 

 instrument: (1) The price is low. (2) Manipulation is simple. 

 (3) The work is rapid, and extremely accurate. (4) There are no 

 delicate working parts which can get out of order, and the whole 

 instrument is easily taken apart for packing, and is very portable. 



The above description refers to the original form of the instru- 

 ment. Later, the Cambridge Scientific Instrument Company ha\v 

 brought out an improved form, at a higher price. For most 

 purposes the original form will suffice. The instrument is said by 

 the makers to cut celloidin objects ; but for this purpose a sliding 

 microtome will certainly be found preferable. 



The Minot microtome, of which a description may be found in 

 the 'Journal of the Royal Microscopical Society,' 1889, p. 143, is a 

 neat instrument designed, like the Cambridge rocker, for cutting- 

 ribbons of paraffin imbedded objects. It is worked on the sewing- 

 machine principle, and cuts very rapidly. But its work is not so 

 fine as that of the Cambridge instrument, possibly on account of in- 

 sufficient compensation in the working parts. This defect is said to 

 have been satisfactorily overcome in the beautiful instrument, con- 

 structed on the same principle, of Reinhold, a description of which 

 may be found in the journal above quoted, 1893, p. 706. The work 

 afforded by this instrument is certainly of the highest order, but 

 the price is against it, as it costs about 201. Both of these instru- 

 ments are said to be able to cut celloidin sections ; but it is self- 

 evident that they are not so well adapted for that purpose as the 

 sliding microtome. 



It is unnecessary here to do more than allude to the large and 

 cumbrous instruments specially designed for cutting sections of 

 brain. Such is the microtome of Strasser, of which a description 

 may be found in the ' Journal of the Royal Microscopical Society,' 

 1892, p. 703, and that of Gudden and others. They are only 

 required for certain very special neurological researches, and are 

 not at all adapted to the wants of the zoologist or histologist in 

 general. For these, we may here repeat, the all-round instrument 

 par excellence is Jung's medium-sized Thoma microtome, No. IV., to 

 which, if lengthy series of paraffin sections be frequently required, a 

 Cambridge rocker may conveniently be added. 



But it is needful also to describe one or more of the best instru- 

 ments designed specially for cutting sections by congelation or freer./ it;/ 

 of the imbedding mass. Dr. R. A. Hayes designed an ether freezing 

 microtome with the object of affording to those who have occasional 

 need to cut sections of tissues for pathological investigations, &c.. 

 the means of doing so quickly, conveniently, and accurately. It is 

 illustrated in fig. 400. It is very compact, solidly constructed, and 

 simple in plan. It freezes rapidly, and permits sections of large 



