Miscellaneous, 311 



Directions for Making and Preserving Microscopical Preparations. 

 -^ By M. Harting of Utrecht. 



[The following directions are translated, in a slightly abridged 

 form, from different parts of Harting' s work on the Microscope*. 

 They have been selected as likely to prove useful to that now numerous 

 class of students who prosecute original researches with the aid of the 

 microscope. Personal experience enables us to attest the value of 

 some of these hints ; and the fact that Prof. Harting' s unrivalled 

 cabinet of microscopic preparations, comprising more than 6000 spe- 

 cimens put up with his own hands, is indebted for its completeness 

 and preservation to the methods of manipulation here described, is 

 sufficient evidence of their excellence. — Trans.] 



^' Very few objects can be preserved unaltered when dry, and even 

 when this is possible, as in the case of hairs, fish-scales, and the like, 

 the method is not to be in general recommended. Such objects, 

 when surrounded by air, possess too little transparency to permit a 

 satisfactory definition of their component parts. It is only for pre- 

 serving the scales of insects and certain test objects that the dry 

 method is useful, and even preferable, from the superior distinctness 

 with which it enables the observer to make out the different sorts of 

 lines upon these bodies. The simplest mode of mounting these scales 

 for microscopical examination, is to lay a few of them upon an ordi- 

 nary glass object-slide, which may be moistened with the breath, if 

 this is found necessary to make the objects adhere to it. A glass 

 covering-plate, of suitable thickness, is then laid upon the object ; 

 and finally there is pasted round both slide and cover a piece of paper, 

 having in its centre an opening corresponding to the position of the 

 object. 



Different specimens from the organic kingdom would, if simply 

 put up in the dry way, speedily become the prey of vegetable and 

 animal parasites. This is the case, for instance, with sections of 

 organs like the lungs, preserved by inflation and subsequent drying. 

 To prevent this disadvantage, I am in the habit of moistening such 

 preparations with oil of turpentine, which, on evaporating, leaves 

 upon the surface a very delicate varnish-like coating, which suffices 

 for its protection. 



Most microscopical objects, however, require to be mounted in 

 some fluid, the nature of which must be varied according to the pro- 

 perties of the substance which it is wished to preserve. The fluids 

 which I employ are the following : — 



I. Saturated Solution of Chloride of Calcium. 

 1st, This solution, which must be perfectly free from traces of 

 iron, is of very general utility, and may be employed in all cases in 

 which the substance to be preserved is of moderate firmness or hard- 

 ness. In this solution all preparations of bones and teeth, sections 



* Het Mikroscoop, deszelfs gebruik, geschiedenis en tegenwoordige 

 tocstand. Utrecht. 3 vols. 1848-50. 



