594 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



the object-carrier is 14 mm. ; the greatest length of the run of the pre- 

 paration along the knife-edge is 11 cm. Any razor can be used in this 

 microtome. 



Fig. 122 



New Freezing Microtome for use with Carbon Dioxide Tanks.* — 

 Prof. C. E. Bardeen has devised a microtome for use with carbon di- 

 oxide tanks. The illustrations show the machine ready for use, and 

 the apparatus in section (figs. 123, 124). The apparatus is supported by 

 the nozzle of the carbon dioxide tank, and the valve of the tank con- 

 trols the escape of gas into the tube K D. From this tube the gas 

 escapes into the chamber beneath the microtome plate, and makes its 

 way out through a spiral passage. By this device the maximum freez- 

 ing power is secured. 



The mechanism for regulating the thickness of the sections consists 

 of a movable wheel I, which moves up and down on a screw-thread, cut 

 25 threads to the inch, one revolution of the wheel, therefore, raising 

 or lowing it a millimetre. The margin of the wheel is divided up into 

 spaces representing 20 microns. The knife slides on glass guides. 



The advantages claimed for this apparatus are that but little carbon 

 dioxide is wasted ; the temperature of the freezing stage can be con- 

 trolled , the machine and tank may be readily carried about. It is simple 

 in design, strong, and unlikely to get out of order. 



* Bausch and I.omb's Cat. B, 16th edition; also Journ. App. Microscopy, iv. 

 (1901) pp. 1320-3 (2 figs.). 



