298 ENTOMOLOGY. 



For staining, alcoholic cochineal (Mayer's formula) is 

 recommended for insects on account of its high penetrating 

 power, since the chitinous skin of insects is but slightly 

 permeable by aqueous solutions of carmine. 



To embed an object, as a small insect, or portion of an 

 insect, make a little tray, box, or thimble out of paper, 

 which can be filled with melted paraffine, the paper being 

 removed before cutting; the cast thus made can be inserted 

 directly in the jaws of a Thoma microtome, or cemented to a 

 piece of cork which is held by them. Besides paraffine, wax 

 and oil and naphthaline serve as embedding-masses. A bit 

 of soft tissue, says Prudden. may be embedded in a mixture 

 of equal parts of white wax and paraffine melted together, 

 with the addition of a sufficient quantity of olive-oil to give 

 the mass the proper consistence for cutting when cold. 



Celloidin is also recommended for use as an embedding 

 material. It may be obtained of dealers in micro-supplies. 

 It is sold in the form of plates and shreds (the shreds 

 being more convenient for use) put up in ounce packages. 

 A saturated solution of celloidin is made in a mixture of 

 equal parts of sulphuric ether and alcohol (97 per cent). 

 This requires about twenty-four hours with occasional 

 agitation. 



If the object to be cut is loose in structure or porous, it 

 should be transferred from strong alcohol to a mixture 

 of equal parts of alcohol and sulphuric ether and allowed 

 to remain for a short time, and then placed in a small 

 quantity of the celloidin solution and allowed to remain 

 until the celloidin has thoroughly penetrated the object. 

 If the piece is small, a drop of the celloidin solution may be 

 placed on one corner of a slightly greasy glass slide, and 

 the object set up in it with the face to be cut placed next 

 the glass. More of the solution is dropped on to the object 

 until it is covered by a lump or pile of the celloidin; when 

 it has set sufficiently to allow it to be handled without dis- 

 placement, immerse the slide with its little pile of celloidin 



