THE ROCKING MICROTOME 37 



Cathcart's Microtome. — An improved form of Cathcart's 

 freezing microtome is made by Messrs. W. Watson and Son, 

 High Holborn, W.C., which is both cheap and convenient 

 to use in practice. The tissue, after ' hardening ' in alcohol 

 (q.v.), is placed on the zinc plate of the microtome together 

 with a little gum-water. Some ether is placed in the bottle, 

 and the bellows worked until the gum has frozen ; more 

 gum solution is added and again frozen, and so on until 

 the tissue is covered and frozen into a solid mass. Fine 

 sections are then cut with a flat ground razor blade, which 

 is kept moistened with alcohol. The bellows are worked a 

 little from time to time to keep the mass frozen. The 

 sections as soon as cut are transferred to alcohol. 



The Booking Microtome. — This machine is made by the 

 Cambridge Scientific Company. It is only used for 

 specimens imbedded in paraffin (q.v.), and is automatic; 

 that is to say, it can be set to cut sections of definite thick- 

 ness, and every time the handle is pulled, a section is cut 

 and the specimen is moved forward ready for another. 



Muencke's Microtome. — Dr. E. Muencke, of Berlin, makes 

 a microtome which indicates by means of a dial the thick- 

 ness of the sections being cut. This is a very useful and 

 convenient form for general purposes. 



The Incubator. — Although the greater number of the 

 saprophytic and many of the pathogenic bacteria grow at 

 the ordinary temperature, yet some of the pathogenic 

 species can only be cultivated at the higher temperatures, 

 and many of those which grow at the room temperature 

 develop more rapidly and vigorously when kept in a warm 

 chamber or incubator at a temperature of from 27° to 38° C. 

 ( = 80° to 100° F.). 



Whenever the ' ordinary ' or room temperature is men- 

 tioned in connection with bacteriological work, a temperature 

 of about 20° C. ( = 68° F.) is understood, while by 'incuba- 



