2500 Journal of Applied Microscopy 



without in any way disturbing the position of the object. The hole is about 

 one mm. in diameter and 5 or 6 mm. from the edge, thus being above the 

 marginal portion of the raised dais which forms the floor of the box. Fluid 

 introduced through the hole is therefore held by surface tension between the 

 two glasses which form the top and bottom of the box, and so is prevented from 

 contact with the metal parts. The use of corrosive reagents (corrosive sublimate, 

 e. g.) is not, therefore, prevented. 



In fixing highly contractile organisms, such as trematodes, for permanent 

 preparations the life box as thus modified is very useful. Such animals usually 

 contract strongly, taking on various unnatural positions immediately upon com- 

 ing in contact with fixing fluid. But a normal position may readily be gotten by 

 putting the animal in the life box in a small drop of water, normal salt solution 

 or other non-irritating medium, and deliberately adjusting the cover until the 

 exact position and degree of compression desired are gotten. Then (not before) 

 the fixing fluid is run in around the animal by means of a small pipette and 

 allowed to act as long as necessary to produce fixation in the position in which 

 the animal is held. When fixation is completed, or, if preferred, as soon as all 

 power of contraction is destroyed, the cover is removed and the animal trans- 

 ferred to a larger body of fixing fluid, or to such other reagent as may be desired. 



The aperture in the cover-glass in no way interferes with the use of the life 

 box for the long continued observation of living organisms, but gives the addi- 

 tional advantage of allowing any desirable position or condition to be made per- 

 manent at will. I know of no other means by which the same result may be so 

 satisfactorily accomplished. W. S. Nickerson. 



University of Minnesota, Department of Medicine and Surgery. 



The Technique of Biological Projection and Anesthesia of 



Animals. 



Copyrighted. 



XVII. DIRECTIONS FOR MOUNTING LIVE ORGANISMS FOR PRO- 

 JECTION. 



These directions are especially applicable to mounts made for use on projec- 

 tion microscopes of the direct type, as illustrated in articles III and V of this 

 series (vol. V, No. 5, Fig. 2, and No. 7, Fig. 4), in which the stage of the micro- 

 scope is in the vertical plane and the pencil of light rays is not reflected by a 

 mirror. Projection microscopes with vertical reflectors offer the one advantage 

 — desirable in a small percentage of all cases — of having the stage of the 

 microscope in the horizontal plane ; but this advantage is offset by loss of light, 

 difficulty of adjustment, and additional expense. All the forms of cells shown 

 in Fig. 9, except Nos. 14, 16-20, which have open tops, may be used on 

 horizontal stages and the organisms are mounted in them as described below for 

 use on the direct type. 



In selecting the size and shape of cell to contain an organism which is to be 



