ZOOLOGY AND BOTANY, MICKOSCOPYj ETC. 153 



engage half a tootli the sections will be 2*5 /* (or 1/10,000 in.) in 

 thickness, a whole tooth 5 /x, and so on. 



The great novelty of the instrument, however, consists in the 

 use of an endless band, 2 in. wide, to receive the sections as 

 they come from the razor. With proper imbedding material the 

 sections will adhere to one another and come off the razor in the form 

 of a ribbon, and as soon as a sufficient length has been cut the end is 

 picked up by a needle or scalpel and placed on the band which is 

 just above the razor (see fig. 31). By the arrangement of cords and 

 rods, shown in fig. 29, the band is adjusted so that at each " throw " of 

 th€ object-carrier (or turn of the fly-wheel) it is moved forward through 

 a distance equal to the breadth of the surface which is being cut. 

 The ribbon of sections consequently travels up the band until the 

 top is reached, when the sections can be cut off in convenient lengths 

 for mounting. 



The directions for using the instrument issued by its manu- 

 facturers, the Cambridge Scientific Instrument Co., have been re- 

 published,* and need not be repeated here. The most important points 

 insisted upon are the sharpness of the razor and the accurate paral- 

 lelism of the sides of the imbedding material from which the sections 

 are cut, so that the ribbon of sections may be quite straight for con- 

 venient mounting. The Company supply special imbedding material, 

 so that sections may be satisfactorily cut within a very considerable 

 range of temperature, obviating the necessity of exactly adjusting 

 the temperature of the room to the specimen of paraf&n in use, or, 

 as an alternative, of providing a number of specimens of paraffin with 

 different melting points. 



The ordinary 3x1 slides are not of course large enough for the 

 ribbons, and slides of double the size (6 in. x 2 in.) are found the 

 most convenient, with cover-glasses 5 in. x 1^ in. On such a slide 

 five or six rows of the ribbons may be placed, each row containing 

 from fifty to one hundred sections or more. 



Beck's Automatic Microtome. — At the January meeting of the 

 Society, Messrs. Beck exhibited a simplified form of the Caldwell micro- 

 tome, the cost of which is a little over a third only of that of the 

 original. 



The new form has an automatic movement and clamp arrangement 

 similar to that of the Schanze (jpost), but to this is added the 

 Caldwell endless band, which is driven by a very simple mechanism, 

 and which has the special feature of being very readily detached from 

 the microtome, so as to leave the latter free to be used for ordinary 

 purposes other than the cutting of series of sections. 



The new microtome will, we think, be found a great desideratum 

 by those who are desirous of having a smaller and less elaborate in- 

 strument, and it will be illustrated in the April part of the Journal. 



Thoma's Microtome.— Prof. E. Thoma sends us some further 

 notes on this subject, and Herr Jung of Heidelberg the woodcuts. 



It often occurs, he says, that in using the microtome, sections of 



* Quart. Journ. Micr. Sci., xxiv. (1884) pp. 648-54. 



