116 



THE MICROSCOPE. 



size. 1 To preserve the brush in a fit state, it should 

 always be cleaned with spirits of wine whenever it has 

 been used." 



Mr. Topping's fluid for mounting consists of one ounce 

 of rectified spirits to five ounces of distilled water \ this he 

 thinks superior to any other combination. To preserve 

 delicate colours, however, he prefers to use a solution of 

 acetate of alumina, one ounce of the acetate to four ounces 

 of distilled water : of other solutions he says, that they 

 tend to destroy the colouring matter of delicate objects, 

 and ultimately spoil them by rendering them opaque. 



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 sup- 

 ported between the two fingers. Fig. 

 76 represents the syringe : a is a cylin- 

 drical brass body, with a screw at the 

 top for the purpose of firmly screwing 

 down the cover 6, 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 con- 

 venience of cleaning ; e is a stop-cock, 

 on the end of which another stop-cock 

 / fits accurately ; and on the end of 

 this either of the small pipes g, which 

 are of different sizes, may be fixed. The 

 Fig. 76. transverse wires across the pipes are in- 



tended 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 



(1) " Coachmaker's Black" is an excellent varnish. 



