LEADED CORK— EVAPORATING -DISH— TEST-BOX, ETC. xxvii 



Leaded cork. — Some structures require to be dissected under water, as, e. </., those 

 of insects &c. These should be fixed with pins upon a piece of cork, beneath which 

 a plate of lead, corresponding in size, has been fastened. In many cases it is advan- 

 tageous to dissect these tissues under the simple microscope. An aperture may then be 

 made in the lead and cork, and the tissue or structure stretched across the aperture, so 

 that the light may pass through it; or it may be illuminated as an opaque object by the 

 aid of the bull's-eye. 



A trough, composed of five pieces of glass cemented together with marine glue, four for 

 the sides and one for the bottom, will serve to hold the water and the leaded cork. 



Evaporating Dish or Saucer. — It is advisable to keep one of these, with a flat bottom, 

 always at hand filled with distilled water, in which slides and covers that have been used 

 may be immersed. The remains of objects which have been examined are thus easily 

 separated from the glasses, and there is but little trouble in wiping the latter clean. If 

 held under a gentle current of water, all remains of tissues or test-liquids may be washed 

 away from the dish — the glasses, from their gravity, remaining at the bottom. 



Test-box. — A wooden box, holding from six to a dozen or more test-bottles, is indispen- 

 sably requisite. The box must be divided into partitions corresponding to the size of the 

 bottles, and the latter must be wedged between these partitions so that the stopper can 

 bo removed without fear of disturbing the bottles. The box should be covered with a lid 

 furnished with hinges, so that no room may be required to place the lid when the box is 

 opened. The bottles will vary in size according to option ; but they should be of at least 

 1-ounce capacity. Each should have a stopper so prolonged as nearly to reach the bottom 

 of the bottle, its form being either conical or fusiform. The advantages of this form of 

 stopper are, that a mere trace or several ordinary drops of the reagent may be applied to 

 the object as required. 11 a very minute quantity be desired, the lower part of the stopper 

 is allowed to touch the inside of the neck of the bottle when it is withdrawn ; and if a 

 larger quantity be required, this proceeding may be avoided. Each bottle should be labelled ; 

 and a label should also be placed upon the upper end of the side or partition of the box near 

 to the bottle, so that the nature of the contents of each bottle may be ascertained without 

 removing it from the box. The general advantages of this apparatus are, that the quantity of 

 reagent required can be obtained to the greatest nicety, and it can be added to the exact spot 

 required with one hand only, so that the other can be employed to hold the slide and object &c. 



Reagents or Test-liquids.— Some of these should be kept in the test-bottles ; but larger 

 quantities should also be kept in other stoppered bottles. We give a list here of those test- 

 reagents which are most frequently required ; the method of preparing each, the strength, 

 &c. will be found under the respective heads. 



1. Sulphuric acid. 2. Nitric acid. 3. Acetic acid. 4. Caustic potash. 5. Chloride 

 of calcium. 6. Aqueous solution of iodine. 7. Oil of turpentine. 8. Glycerine. 9. Acid 

 nitrate of mercury (Millon's test-liquid). 10. Distilled water. 



Benzole and alcohol or methylated spirit should also be kept at hand. Chromic acid 

 should be preserved in a wide-mouthed stoppered bottle, and its solution prepared when 

 requisite, as it easily becomes decomposed by dust &c. 



Troughs are flat, oblong glass boxes, without lids. They are made of pieces of glass 

 cemented together by marine glue, and are used in examining the larger aquatic plants or 

 animals in a living state, also in mounting objects. 



