208 



THE AMERICAN MONTHLY 



[November, 



li found to require cleaning, it 

 can be done with needles and a 

 brush as in ordinary cases. If clean 

 but not transparent, warm and set 

 away imder a bell-glass until it is 

 tit to mount, making another change 

 of acid if necessary. In all cases 

 it is best to take the last change of 

 acid from a bottle kept specially 

 clean and pure for that purpose. 

 Objects macerated in acetic acid 

 can be treated in the same way. 



Dropping tubes. — The most con- 

 venient way of applying fluids and 

 reagents in microscopical work that 

 I am acquainted with is to pass a com- 

 mon " medicine dropper " through 

 the cork of the bottle containing 

 the fluid used. This idea is not 

 original, I 8a\^ it in some publica- 

 tion, I do not remember where, but 

 it deserves renewed notice. I have 

 used such a medicine dropper to 

 hold and apply glycerin jelly, with 

 great Satisfaction. It is iilled from 

 the general supply while warm, and 

 after cooling is litted into the cork 

 of an empty bottle where it is kept 

 while not in use, so as to avoid dust 

 and mould. The small quantity in 

 the dropper is quickly Avarmed over 

 the lamp when needed, and just 

 enough can be put on the slide 

 without causing any air-bubbles. 

 Several slides can be mounted from 

 the dropper without relilling it. 

 Tubes longer than a medicine drop- 

 per, drawn to a very fine orifice and 

 capped with the bulb of a medicine 

 dropper are also very convenient 

 for innumerable purposes. 



Wax-cells. — So much has lately 

 been said about wax-cells that I 

 think a little more cannot be amiss. 

 I have some that are utterly de- 

 stroyed, and more that are very 

 much injured by the deposit on the 

 under side of the cover. The worst 

 of these were mounted by one who 

 was given to using turpentine to 

 soften the wax ; this is probably 



the cause of the deposit in these 

 slides. My own mountings are very 

 free from this trouble, although all 

 made w'ith wax-bottomed and as- 

 phalt-covered cells. I think the 

 reason of this is that my cells are 

 mostly made a long time before 

 they are used. My business is such 

 that I can only devote time to mi- 

 croscopy in the mornings and even- 

 ings. Hence most of my work is 

 interrupted by twelve-hour inter- 

 vals. To save time I make up a 

 lot of cells at once, using double 

 thick pond-lily wax and brass cur- 

 tain rings, sometimes a little fiat- 

 tened. To make the cell, I place 

 the ring on the wax and press it 

 down with a slip, then with a wet 

 penknife blade, I cut around the 

 ring outside and lift it out. The 

 disc of wax is then punctured from 

 below with a needle in 2 or 3 places 

 near the middle, and if not already 

 raised a little in the centre, it is 

 gently bent with the finger, so that 

 when placed on the slide it will 

 touch only at the edges. The ring 

 is now placed on the centre of a 

 slip in the turn-table, and gently 

 pressed to make it adhere. Then 

 removing the slide it is held over a 

 lamp, keeping it level ; the wax 

 first softens at the ring aiul as the 

 softening proceeds towards the cen- 

 tre, the air escapes through the 

 needle holes and blisters are pre- 

 vented as the wax settles down 

 upon the slide. l>efore the wax 

 actually melts, the slide should be 

 removed and returaed to the turn- 

 table to see if it is still centered. If 

 the wax does melt, no harm is done 

 unless the ring slides from its place 

 before it cools. When cool the ring 

 is firmly fixed and it is then coated 

 on the turn-table with Brunswick 

 black, though perhaps shellac would 

 be safer from liability to the " sweat- 

 ing." Having prepared from 4 to 6 

 dozen cells of different sizes, they 



