448 XXXII. CELL-DIVISION AND NUCLEAR DIVISION. 



tures. The lowest division, made of sheet iron, serves as a hot 

 chamber. Upon this rests a double-walled copper case, into the 

 water between the walls of which, and inserted through a tube, is 

 an automatic thermo-regulator, by which the temperature of the 

 water can be maintained at 55 C. or higher. Lastly, on the 

 copper case rests another chamber made of sheet iron, without a 

 bottom, provided with a door, and with sides made of glass. A 



FIG. 157. F. Rosen's paraffin oven and warm chambers. 



thermometer inserted from above shows that, when the tempera- 

 ture of the middle chamber stands at 60, that of the upper 

 chamber is from 32 C. to 36 C. By means of a slide which 

 opens air-holes this temperature can be regulated. The copper 

 top of the middle chamber has approximately the same tempera- 

 ture as in the middle chamber itself, but by laying pasteboard 

 upon it, it can be lowered to about 48 C. The entire height of 

 this paraffin oven is about 24 inches ; its breadth 11 inches. 



With an obliquely-placed razor only single sections can be 

 taken ; with a straight razor a series of successive paraffin sections 



