SECTIONING AT A TEMPERATURE OF 25 FAHRENHEIT. 283 



FIG. i. The above figure is drawn to scale one eighth full size. A, exterior of 

 copper box. , ice chamber. C, plate glass 3{ inch thick, forming the top of 

 operating compartment D. D, operating compartment The work table on which 

 the microtome is placed forms the bottom of the operating compartment, which has 

 the same area as the plate glass top, C. A thermometer is suspended in the compart- 

 ment just above the microtome. This is done by glueing two loops of tape to the 

 plate glass cover C and slipping the thermometer through these loops. We sometimes 

 place a second thermometer on the bottom of the operating compartment, but the 

 temperature registered by the one near the knife is the proper guide. , heavy sheet 

 rubber, which is kept in place by the copper frame, f, and copper bolts, G. F, 

 copper frame. G, copper bolts which pass through the frame F, sheet rubber, E, 

 and air chamber, N. The free ends of these bolts with nuts are in the operating 

 compartment, D. ff, hand holes in the heavy sheet rubber. The outer broken 

 circle indicates the larger holes through the copper air chamber, N, and these must 

 be large enough to admit the forearm freely. The hand hole, H, in the sheet rub- 

 ber, must, on the contrary, be small enough to clasp the wrist tightly, to prevent 

 escape of cold air from the operating compartment D. The sheet rubber must be 

 renewed at least once a year, or as often as it becomes hard and loses its elasticity. 

 When not operating the microtome, the hand holes, H, must be tightly closed with 



