The Microscope. 181 



come in contact with any other parts of the machine. This tray fits 

 into a recess in the side of the bed-plate of the instniment just 

 below the knife, and into this tray the celloidin sections may be 

 allowed to drop as fast as cut. 



The paraffine-holders are square and seven-tenths of an inch in 

 diameter, so that a block of that size may very readily be sectioned. 

 For the botanist, one of these holders is provided with a movable 

 side and screw for clamping objects, so that rather tough stems may 

 be firmly held between blocks of cork, while the more delicate 

 vegetable tissues, or such as must be embedded in fresh carrot, 

 soaked in gum and hardened in alcohol, may also be firmly held for 

 sectioning by the same device, provided the pieces of carrot are first 

 trimmed into the right shape. The same style of holder is equally 

 applicable for holding the corks — if properly trimmed — upon which 

 tissues are embedded in celloidin or in gum. This style of holder 

 also enables one to embed very long objects entire in parafiine, — 

 such as earth-worms, — and to cut them as a single piece, provided 

 the surrounding parafiine is carefully trimmed so as to have two oppo- 

 site sides parallel. An object six inches long and three-fourths of an 

 inch in diameter embedded in this way may be cut into an absolutely 

 continuous series of sections without losing any essential portions. 

 This is accomplished by slipping the block through the quadran- 

 gular clamp for the distance of half an inch every time a half -inch 

 of the object has been cut ofP in the form of sections. One-half 

 inch is the length of block which can be cut at one time without 

 readjusting the feed-screw which moves the block and vibrating 

 lever over towards the knife, the whole being kept firmly in place 

 against the face of the hollow screw by a strong spring which 

 presses against the end of the trunnion on the outside of the iron 

 pillar on that side of the instrument where the knife is fastened, so 

 that all the sections are of exactly the same thickness from first to 

 last. Cutting up large objects in the manner above described is not 

 possible with any other form of microtome yet constructed. 



Almost any section-knife, — wide, or narrow-bladed, — will fit 

 into and be firmly held by the knife-clamp, which is, however, 

 intended more especially to hold an ordinary razor. The best razors 

 for cutting sections have been found to be those of the best make 

 only, such as Wade & Butcher, or Joseph Rodgers & Sons, of Shef- 

 field. Only such razors as hold an edge well should be used. 



For ribbon -cutting by the parafiine method the block contain- 

 ing the object, after it is trimmed and soldered to the parafiine with 



