METHODS OF STUDY 9 



out through this opening. For this purpose a straight needle and one 

 with the tip bent at right angles to the shank are most useful. Upon the 

 care with which this operation is performed, including the careful flat- 

 tening out of the body in the most favorable position for study, will 

 depend much of the value of the mount. It should be remembered that 

 the body contents will take the stain and if not thoroughly removed will 

 more or less obscure the characters that it is necessary to see. 



Trouble is frequently experienced at this point due to the formation 

 of hard, white lumps either within the body or partially encasing it. Ap- 

 parently these lumps are formed by the combination of the caustic potash 

 with the body fats and there seems to be no way by which their formation 

 can be prevented. However, they are readily soluble in carbol-xylene 

 and may be removed by placing the specimens in a small amount of 95% 

 alcohol containing a few drops of this reagent. This should not be done, 

 however, until the specimens have been 'cleaned as thoroughly as possible, 

 as the alcohol hardens the body contents and makes them difficult to re- 

 move. The carbol-xylene should be washed out in 95% alcohol before 

 the specimens are placed in the stain. If difficulty is not experienced with 

 the formation of such lumps the specimens may be removed to the stain 

 directly from the water in which they are washed. 



The stain which I have used is Magenta and I cannot speak in regard 

 to the action of any of the others that have at times been recommended. 

 This stain may be procured in liquid form. The strength of the solutions 

 obtained seems to vary somewhat, but there appears to be very little, if 

 any, difference in their staining qualities and they can sometimes be much 

 diluted with water. Staining is best carried on in deep hollow slides 

 having a ground-glass surface upon which data may be written. These 

 should be covered with a coverglass and the stain allowed to run out 

 under this. The evaporation of this stain under the coverglass will seal 

 a slide so effectively that it may sometimes remain for days without 

 drying out. 



Usually a half hour is sufficient to give a stain as good as can be 

 obtained, this having been demonstrated by numerous experiments. The 

 specimens should then be removed to 95% alcohol in which the excess 

 stain is washed out, then placed for a moment in carbol-xylene (three 

 parts xylene to one part carbolic-acid crystals) and then mounted in 

 balsam. If the staining has been effective the resulting mount should 

 show all spines and chitinized areas of a bright red, while the remainder 

 of the derm is perfectly clear. 



As I have said, the general method is simple enough, but care in 

 numerous details which one can only learn from experience is necessary 

 to get the best results. Above all care must be taken that the specimens 



