WITH THE MICROSCOPE. 79 



needles, or small knives, and forceps. If the preparation has been 

 preserved in spirit or other solution, it must be dissected in the same 

 fluid, but in ordinary cases clear water may be used. The micro- 

 scopist should be provided with a few small dishes, varying in size, 

 and about an inch or more in depth. The large built cells, pi. XVIII, 

 figs. 109, no, make very good troughs for dissecting in, but small 

 circular vessels are made on purpose. 



145. Loaded Corks. The object to be dissected is attached to a 

 loaded cork by small pins, pi. XXI, fig. 134. We may take a piece 

 of flat cork rather smaller than the cell, and then cut a piece of 

 sheet lead somewhat larger than the cork. The edges of the lead 

 are then folded over the cork and beaten down slightly with a 

 hammer, and may afterwards be filed with a rough file. 



The object being fixed upon the cork and placed in the cell, fluid 

 is poured in until it just covers the surface, pi. XXI, fig. 133. A 

 strong light is then condensed upon it by means of a large bull's-eye 

 condenser, or by a large globe full of water. I have always found 

 that delicate dissections could be made with the greatest facility 

 without the aid of a dissecting microscope, provided a strong light 

 was condensed upon the object. Occasional examination of the 

 dissection with a lens of low power is advantageous ; but if a lens 

 be employed during the dissection there is great danger of acciden- 

 tally injuring the specimen, as it is impossible to judge of the distance 

 which the needle point may be beneath the surface of the fluid. 

 Minute branches of nerves or vessels may in this way be followed 

 out, and small pieces of the different tissues into which they can be 

 traced may be removed for microscopical examination with a pair of 

 fine scissars, pi. XV, fig. 82. Membranes may be dissected from the 

 structures upon which they lie in a similar manner. By this plan the 

 nervous system of the smallest insects can be readily dissected. The 

 mode of proceeding is represented in fig. 133. 



14O, Tablets upon which Dissections may be Pinned out. Many 

 preparations require to be arranged in a particular position previous 

 to being mounted as permanent objects. Sfal>s of wax are usually 

 employed by anatomists for this purpose, but when transparency is 

 required the dissections may be attached by threads to thin plates of 

 mica. 



I have found that the best slabs may be made of a mixture of 

 max and gntta percha, in the proportion of one part of the former to 

 two of the latter. The ingredients are to be melted in an iron pot, 

 over a clear fire, and well stirred. When quite fluid, the mass may 

 be poured upon a flat slab and allowed to cool. Thin cakes of 

 about the eighth of an inch in thickness are thus obtained, and they 



