COMPOUND MICROTOMES. 451 



by means of a glass rod, and allowed to dry in a vertical position. 

 The microtome sections are laid on water at 40 C. in a large 

 dish, a prepared object-slide pushed flat under them, and the 

 sections lifted out. They are then dried at 35 C., the paraffin 

 removed with xylol, and this latter with absolute alcohol. 



The Compound Microtome. While, until recently, microscopic 

 sections were almost always cut with the hand, and of microtomes, 

 at any rate, only the simple hand microtomes were in use, now the 

 compound microtome is found in all botanical laboratories. Every- 

 one, therefore, who wishes to work with success in the higher 

 reaches of histology must now acquire a knowledge of its mani- 

 pulation. The number of good microtomes manufactured by 

 various mechanicians is now very large. Most of them have their 

 partisans, and most workers tend to declare that microtome the 

 best to which they themselves are accustomed. In construction 

 the different microtomes which are now in use are distinguished 

 from one another in that with some the razor and the object to 

 be cut move on approximately horizontal slides, in the others 

 there is a horizontal carrier for the razor and a vertical one for 

 the object, and with still others the razor is fixed and the object 

 is carried against it. 



For some years we have used the Thoma-Jung sliding micro- 

 tome, 1 and have found that it has thus far answered all the 

 demands which we have made upon it. These microtomes do 

 not work so rapidly as many others, but in respect of certainty of 

 action, and the uniformity in thickness of successive sections, can 

 scarcely be surpassed. Chving to the complicated structure and 

 difficulties in use of this and other large microtomes, we will confine 

 ourselves to a single pattern, issued at a not too high price ; pre- 

 mising, however, that there are others w r hich work equally well, 

 and some possibly even more perfectly. It is naturally best to 

 learn the art of manipulating a microtome under the practical 

 guidance of a teacher, as mere descriptions are a very poor aid. 



The Rocking Microtome The microtome most used in Great 

 Britain is perhaps CaldwelPs Booking Microtome, made by the 

 Cambridge Scientific Instrument Company, which is illustrated in 

 the adjoining Fig. 159, where its construction is readily recognis- 

 able. Upon a massive base plate are two strong uprights, made 

 in the same casting ; that upon the left hand serving to carry, by 



1 The Thoma-Jung microtomes can be obtained through W. & J. George. 

 Limited (successors to Becker & Co.), London and Birmingham. 



