520 SUMMAEY OF C3UBRENT EESEAROHES RELATING TO 



can move freely in every direction except the vertical, and are always 

 in focus. The air channel also serves to hold any excess in the amount 

 of fluid, above that required to fill the area of the circular field. 

 Infusoria may also be isolated and sealed up, when they may be 

 kept alive and in good condition for a week or more. In some tem- 

 porary slides, where the air-space was much too small, there being no 

 channel, rotifers, amoehse and other forms, were alive and active for 

 nearly a week. 



Beeswax alone seems the best cement for sealing. If put in a 

 syringe having a very small nozzle, and warmed, the wax may be forced 

 out as a long, thin thread. This can be wound on a spool and kept 

 ready for use when a slide is to be sealed up. A piece long enough 

 to fill the outer channel is placed therein. A glass slip placed over 

 the cover-glass, and pressed down securely, seals the cell, and, as the 

 wax is soft, the stratum of fluid can be made as thin as desired. 



Watson's Reversible Compressor. — Mr. G. Watson's apparatus 

 (fig. 104) consists of a base-plate carrying a compressor which can be 



Fig. 104. 



completely rotated on its horizontal axis — so as to exhibit the object on 

 both sides or even in an intermediate position — as well as on the 

 vertical pin which fits into the socket of the base-plate. The two 

 plates of the compressor are separated by a screw acting against a 

 spiral spring, while the upper one pivots over the lower to allow the 

 object to be inserted. 



Ruled Plate for Measurement of Blood-corpuscles.* — Prof. W. A. 

 Rogers describes a plate ruled in 1,300,000 squares which when 

 not in use is covered in order to protect the filling of the lines. 

 Whenever it is to be used, it is uncovered and the lines filled with 

 graphite by rubbing the surface diagonally with a camel's-hair brush 

 pressed upon the glass with the fingers. A very slight amount of 

 powder upon the brush will be sufficient. After the lines are filled, 

 the blood placed directly upon the slide will not interfere with their 

 visibility. When the examination is completed, the surface of the 

 glass should be cleaned with cotton. 



* 11th Ann. Rep. Amer. Postal Micr. Club, 1886, p. 13. 



