446 E. A. MINCHIN ON SOME DETAILS IN THE ANATOMY OF 



round cover-slips would be in contact with tbe watch-glass round 

 their whole edge, and be very troublesome to lift up with the 

 forceps or in any other way. 



Sometimes the object comes away loose from the cover-slip in 

 the sublimate-acetic. When this annoying event takes place,, 

 put the cover-slip into a watch-glass and cover it with 30 per cent, 

 alcohol; then draw up the object from the sublimate-acetic 

 mixture with a glass pipette of sufficiently wide calibre and place 

 it on the upper surface of the cover-slip in the alcohol. Then lift 

 up the cover-slip carefully with a forceps, taking care the object 

 does not float off the cover-slip to one side or the other, but 

 remains stranded on the cover-slip again. Then drain off the 

 alcohol, invert the cover-slip, and drop it face downwards into 

 50 per cent, alcohol in another watch-glass. This time the 

 rebellious object always sticks to the cover-slip. In all cases the 

 cover-slips should be handled delicately while in the sublimate- 

 acetic or in the weak alcohols, since a too violent jerk may 

 dislodge them ; but I have never known an object to come loose 

 after it has got so far as the 70 per cent, alcohol. 



I have described this method in full detail because I have 

 found it extremely useful for making permanent preparations 

 of dissections. In the flea, for example, it is very easy to dissect 

 out and mount in this way the entire male reproductive system, 

 from testes to penis, and so display every detail of it ; and since 

 the preparation is adherent to the cover-slip, any powers of the 

 microscope, even immersion lenses, can be focused on to it for 

 study of minute details. The principle of the method is that 

 cellular tissues, having been pressed firmly but gently against 

 the glass by capillary attraction, adhere to the glass by their 

 own stickiness ; and when the preparation has been well fixed 

 and hardened, the coagulation of the albumins glues the organs 

 so firmly that they cannot be detached without breaking 

 them. Naturally this does not apply to chitinous organs, 

 which are not wetted by water, and can never be made to stick 

 in this way. 



The preparations, after having been fixed and hardened, can 

 be mounted unstained, or can be stained first in any way desired.. 

 Unstained preparations are best for showing internal details of 

 the chitinous cuticle or skeleton ; stained preparations for 

 showing the cellular structure of the tissues and soft parts ; the 



