LIVE-BOX AND GROWING-SLIDE, ETC. xxiii 



the upper and a plano-convex lens at the lower end. It is screwed into the diaphragm of 

 the body of the microscope, or that of the draw-tube. It erects the images of objects, and 

 serves, with a low object-glass, to reduce the magnifying power at pleasure, and to 

 facilitate dissection under the microscope. 



Live-Box and Growing-Slide. — The live-box is an apparatus in which portions of liquid 

 containing infusoria and other small animals or plants can be confined so as to prevent 

 evaporation and allow of their being watched in a living state. 



A better apparatus, however, fur this purpose is my growing-slide. This consists of a 

 piece of stout plate-glass, 5 inches long and about 2 wide. A circular aperture, of about 

 the diameter of a test-tube, is made near one end ot it. A little glass cup, formed of a 

 portion of a test-tube cut off three fourths of an inch from the closed end, and slightly less 

 in diameter than the aperture, is then fitted into the latter, either by pieces of cork, or 

 by a rim consisting of a glass ring forming a neck to the cup, or in any other way. The 

 cup should project about one fourth above the surface of the slide ; and at one portion of 

 its margin a little groove should be ground, in which two or three threads of a lamp-wick 

 can be placed. The cup should be covered with a circular plate of thin glass, larger than 

 its mouth, and prevented from falling off by a disk of cork fitting the mouth and fastened 

 to the plate by marine glue ; or the cup may be closed with a common cork, the only ob- 

 jection to this being that the mouth of the cup is apt to split. The manner in which the 

 slide is used is this : — Supposing it is wished to follow the changes undergone by some 

 minute alga or infusorium which has been detected in a drop of liquid, it is placed upon a 

 slide and covered with thin glass ; the slide is then placed upon the growing-slide in such 

 manner that the longer dimensions of the two are in the same direction ; a little ledge 

 consisting of a strip of glass fastened by marine glue to the growing-slide will serve to rest 

 the slide against, and prevent its becoming displaced. Distilled water, mixed with a small 

 proportion of the water in which the organism was living before being transferred to the 

 slide, is next put into the cup, and a few threads of lamp-wick cotton, thoroughly moistened 

 with distilled water, are then so placed that one end is immersed in the cup whilst the 

 other is brought into contact with the edge of the liquid in which the object is immersed. 

 Thus, as the water evaporates from beneath the thin glass, the threads will afford a con- 

 tinuous supply, and the threads will not become dry until the whole of the liquid in the 

 cup has become absorbed by them and evaporated. In 'this way we obtain the requisite 

 conditions for the continued gTowth of aquatic organisms. Care must be taken, however, 

 that the thin glass presses but slightly upon the object, and that the threads come as little 

 as possible into contact with the portions of the slide lying between the cup and the thin 

 glass. If the thin glass cover to the cup fit tightly, and the thread be passed through the 

 notch in the cup, no loss will take place by the direct evaporation of the liquid in the cup. 

 In many cases a modification of this slide is arranged so that organisms can be kept 

 in a warm liquid; this is very useful in examining amoeboid movements of the blood- 

 corpuscles, leucocytes, &c. Several varieties of this have been devised (Gkowing-Slide). 

 Compressor, an instrument for the regulated compression of a minute object, The same 

 effect can be produced by a well-made live-box, or by pressure directly applied to the thin 

 glass covering an object by the handle of a mounted needle. 



Cabinet. — A box or cabinet, containing a number of drawers, will be requisite for holding 

 the objects. Each drawer should be numbered or labelled to facilitate reference. The 

 objects should lie fiat in the drawers, so that each may be found when required without 



