84 



THE MICROSCOPE. 



may be required to make the creosote and naphtha into a paste before 

 adding the water : let it stand by a day or two, then filter through white 

 blotting-paper. Add to this solution two small lumps of camphor, and 

 stand it by for a week. At the end of that time filter again through 

 clean blotting-paper. This is an excellent fluid for mounting all vege- 

 table substances in, and many of the more delicate animal tissues keep 

 very well in it ; it has also the advantage of not dissolving the cement 

 used in making the cells. 



INJECTING MINUTE VESSELS. 



For minute injections the most essential instrument is a proper 

 syringe. This is usually made of brass, of such a size that the top of 

 the thumb may press on the button at the top of the piston-rod when 

 drawn out, while the body is supported between the two fingers. Fig. 65 

 represents the syringe : a is a cylindrical brass body, with a screw at 

 the top for the purpose of firmly screwing down the cover b, after the 

 piston c is introduced into it; this is rendered air- 

 tight with leather ; the bottom of the syringe d also 

 unscrews for the convenience of cleaning; e is a 

 stop-cock, on the end of which another stop-cocky 

 fits accurately ; and on the end of this either of the 

 small pipes g, which are of different sizes, may be 

 fixed. The transverse wires across the pipes are 

 intended to secure them more tightly to the vessels 

 into which they may be inserted with thread, so that 

 they may not slip out. In addition to the syringe, 

 a large tin vessel, to contain hot water, with two 

 or three lesser ones fixed in it, for the injections, 

 will be found useful. 



To prepare the material for injecting: Take 

 of the finest and most transparent glue one pound, 

 break it into small pieces, put it into an earthen 

 pot, and pour on it three pints of cold water ; let 

 it stand twenty-four hours, stirring it now and then with a stick ; then 

 set it over a slow fire for half an hour, or until all the pieces are 

 perfectly dissolved skim off the froth from the surface, and strain 

 through a flannel for use. Isinglass and cuttings of parchment make 

 an excellent size, and are preferable for very particular injections. 



The size thus prepared may be coloured with any of the follow- 

 ing: 



