296 ENTOMOLOGY. 



should be employed in all cases, and it should be changed 

 as often as any cloudiness arises in it. Washing-out is done 

 with 70 per cent alcohol, and warm alcohol extracts the 

 acid much more quickly than cold. 



Embedding, Staining, and Cutting. — The water having 

 been completely removed, the object is placed in good 

 chloroform for a few minutes until saturated. The chloro- 

 form, adds Lee, is now to be gradually saturated with 

 paraffine. "This is done by placing it, with the object, on 

 a water-bath, heating it to the melting-point of the paraffme 

 employed, and dropping into it from time to time small 

 pieces of paraffme. When it is seen that no more bubbles 

 are given off from the object the addition of paraffine may 

 cease, as that is a sign that the paraffine solution has en- 

 tirely taken the place of the chloroform in the object. This 

 displacement having been gradual, the risk of shrinkage of 

 the tissues is reduced to a minimum. The heating is then 

 continued (at the melting-point of the pure paraffine) until 

 the whole of the chloroform has been driven off, which may 

 be conveniently tested by the smell." The object is then 

 embedded in the desired position, and sections cut with the 

 microtome. 



The sections, cut dry. are mounted in series on a glass slide. 

 To fix collodion sections in serial order, preparatory to 

 mounting, Minot advises their arrangement on the slide in 

 95 per cent alcohol. Then the alcohol is poured off, and 

 a drop of alcoholic shellac placed on each section (just 

 enough to cover the section completely). The slide is next 

 placed in the oven of a water-bath at 40° for a few minutes 

 (5-10), until dry. The sections are then ready for clarify- 

 ing in clove-oil, and mounting in balsam. 



Another and perhaps better collodion fixative is that 

 tried by Schallibaum, whose solution is prepared by dis- 

 solving one part collodion in three or four parts clove 

 oil, which is applied to the slide by means of a fine brush 

 at the time of using. The sections having been arranged, 

 the slide is warmed for a few minutes (5-10) in the oven of 



