2598 Journal of Applied Microscopy 



box, on the opposite side of the card and carefully slip the card out from between 

 them, and the insect is securely enclosed. The cover of the life box may be 

 slipped down on the insect so as to hold it in one position if desired ; but the 

 cover of the cell should be held in position by rubber bands arranged close ta 

 the edge, and the insect is able to walk, or even to attempt flight, in the cell. 



Organisms of any kind, when mounted in air as above described, cannot 

 endure as intense a degree of heat without injury as those mounted in water. 

 As a rule, therefore, it is necessary to place them in the light at such a distance 

 from the principal focus of the condensing lenses that the heat will be moderate 

 and the light sufficient for the low power objectives which the depth of the cell 

 and size of the organism require. Much excellent work is possible with no 

 higher power lens than ordinary quarter or half-size projection lenses used for 

 lantern slides. A common house-fly may be mounted in a life box and projected 

 with a one-inch objective. With an enlargement up to from six to ten feet in 

 length, it is an interesting and instructive object, as it exhibits its characteristic 

 motions of legs, the cleaning of the wings, and action of the mouth parts. 



XX. DIRECTIONS FOR MAKING AND USING LARGE COMPRESSOR-CELLS. 



Animals having more or less cylindrical bodies, e. g., earthworms and leeches,^ 

 need to be flattened by compression in order that the details of their anatomical 

 structure may be clearly seen under the microscope while they are alive and 

 have not been dissected. In an earlier article in this series, No. X, Jan. 1903,. 

 a simple gravity-compressor for use on a horizontal microscope stage was de- 

 scribed and illustrated. For use on the vertical stage of a projection microscope 

 and whenever more pressure than that produced by gravity is needed, a com- 

 pressor-cell (Fig. 9, No. 15) is useful. This compressor-cell is not on the market 

 in its complete form, but is easily made. As used by the writer, it consists of a 

 compressor (B. & L. Opt. Co. No. 1264) with the following additions : A spiral 

 spring is placed on the screw at the fixed end of the metal plates for the purpose 

 of keeping the upper metal plate up against the screw when the plate is swung 

 around to permit the removal or introduction of the glass plates. This spring 

 is not absolutely necessary, but it increases the ease and speed in handling. 

 To convert the compressor into a cell of adjustable depth, thin sheet rubber, such 

 as is sold for repairing inner tubes of bicycle tires, is cut to the size of the glass 

 plates and about one-fourth of an inch wide. These gaskets are cut through on 

 one of the long sides to allow any excess of liquid to escape during compression 

 of an animal. In place of the gaskets a soft rubber tube may be drawn over a 

 small copper wire and then bent into the form and dimensions of the glass plates,, 

 but this arrangement is not as adjustable as that with gaskets. 



To mount a worm in the compressor-cell place the animal on the lower glass 

 plate and build up on the plate as many gaskets as necessary to prevent too 

 much compression when the screws are tightened. With earthworms the total 

 thickness of the gaskets should be a little more than half the diameter of the 

 specimen. Fill the space within the gaskets and around the worm with water, 

 or chloretone solution if the worm is anesthetized, and place the upper glass 

 plate in position. Adjust the upper metal rim and tighten the screws equally so 



