CHAPTER VI
EXAMINATION OF MARINE OBJECTS—DISSECTION
An enthusiastic observer of nature will learn much concerning the structure of natural objects with the unaided eye, but there are times when he will desire some kind of magnifier to reveal more perfectly the structure of minute parts, or to enable him to observe the small creatures that are invisible to the naked eye. Further, one may learn many interesting and instructive facts relating to animal and plant life by cutting sections for close examination, or by making such simple dissections as will enable one to observe the more salient features of internal structure; we therefore propose in the present chapter to make a few remarks and suggestions regarding work of this kind.
A pocket magnifier is of great value to the young naturalist, both for the inspection of natural objects while engaged in out-door work, and for the subsequent examination of the specimens collected for study. It is often necessary to enable one to identify and classify small animals and plants, and will be in constant demand for the purpose of studying the less conspicuous external features. Such an instrument should be regarded as an essential companion of the naturalist, and should accompany him on every ramble.
There are several different forms of pocket lenses, but for general work there is, perhaps, nothing more convenient and serviceable than the ‘triplet’ magnifier. It is a combination of three lenses, enclosed in a pocket case, and so arranged that they may be used separately or in combination, thus supplying a variety of powers. The three lenses of the triplet are themselves of different magnifying powers, and these powers may be increased by combining two or all of them.
For work at home a ‘dissecting microscope’ is very useful. This consists of a magnifying lens, mounted on a support over a surface on which small objects may be examined and dissected, the height of the lens being, of course, adjusted according to its focal distance. Lenses ready mounted on adjustable stands may be purchased for this purpose, but no one ought to experience much difficulty in designing and constructing some simple stand that will give every satisfaction.
The arrangement just described is, of course, suitable for the dissection of only small objects, and these are placed on a material adapted to the nature of the work to be done. Thus it is sometimes convenient to place the object to be examined on a small sheet of cork, in order that it may be secured by means of pins while the dissection proceeds, while at other times it is essential that it be laid on a hard and unyielding surface, such as that of a slip of glass. But whatever be the nature of the substance on which the dissection is made, its colour may be regulated according to that of the object. If, for example, we are dissecting a small white flower on a piece of cork, we should naturally blacken the cork, or cover it with a piece of dead black paper; or, if we are to dissect a small, light-coloured object on a glass surface, we lay the glass on black paper.
