216 



THE AMERICAN MONTHLY 



[July, 



unate to get this contact with a most agreeable teacher of 

 biology. 



MICROSCOPICAL APPARATUS. 



Automatic Microtome. — This new instrument has been 

 devised by Professor John A. Ryder, of the Biological Depart- 

 ment of the University of Pennsylvania, in order to facilitate 

 the preparation of sections for large classes, and also for the 

 rapid preparation of series of sections in ribbons in embryolog- 

 ical work, in which the element of time becomes a serious con- 

 sideration. The device is small and comj^act, and is also auto- 

 matic — that is, the same movement which cuts the section a 'so 



One-half size. 

 brings the block into position for cutting the next successive 

 section, and so on continuously, of any desired uniform thick- 

 ness the cutting takes place as fast as it is possible to move a 

 vibrating lever up and down through a distance of three inches 

 with the right hand. Nearly all other automatic microtomes 

 are costly, unwieldly, large and heavy, or else very complicated 

 and liable to get out of order. The only exception in part to 

 this rule is the Rocking Microtome, made in Cambridge, En- 

 gland; but it cuts in an arc, so that the sections are segments 



