STERILIZATION. Iol 
in all parts. It also furnishes a maximum temperature with a minimum con- 
sumption of gas, hot air being fed to the flame. The apparatus has an inner, outer, 
and-middle wall. A horizontal iron gas pipe, of the relative size shown in the front 
of the picture, passes entirely around the apparatus at the bottom between the outer 
and middle wall. On top in this tube are many small openings through which 
gas escapes and when lighted forms so many small Bunsen flames. Air is drawn 
in at first and mixed with the gas in the middle open part of the feed 
pipe infront. ‘The products of combustion escape through the chimney 
on top of the oven. ‘There are pilot lights, so that the apparatus is set 
going easily. ‘The result of this arrangement is that the middle wall 
becomes heated very hot, and consequently the air between this wall 
and the inner wall rises, cool air entering through holes in the bottom 
to take its place. ‘There is thus created a powerful upward mount of 
hot air. ‘This enters the oven through several hundred holes in its 
ceiling, is forced downward and escapes through as many holes in the 
floor. From this place the hot air is continually crowded sidewise and 
backward through brass tubes 
into the furnace chamber where 
it serves to support the com- 
bustion. 
Unless the dry-oven has a very 
uniform temperature through- 
out, so that there is no danger of 
scorching the cotton, plugged 
test-tubes should be tied together 
loosely and stood-on. end, cot- 
ton uppermost. Petri dishes 
‘(wrapped in paper as directed) 
may be set on edge. If the 
test-tubes have been properly 
cleaned, dry-heating is not 
necessary for such as are to hold 
steam-heated media, provided 
the cotton used for the plugs is 
dry-sterilized in advance. ‘The 
best surgeon’s absorbent cotton 
is not too good for this work. It should be unrolled and put into the dry-oven in a 
loose armful and heated just below the scorching point for several hours (2 to 3 hours 
at 145° C. will answer), with occasional unfoldings and’ turnings so that all parts 
may be heated uniformly. It is now taken out, re-rolled and put away in clean 
paper until needed. By this means all fungous spores lodged in it are destroyed and 
*F ic, 86.—Dr. George Meyer’s hypodermic syringe, made by Lautenschliger. Desirable on account 
of perfect workmanship, and because it is easily sterilized without injury. This size holds Tce, By 
twisting the button of the piston the packing at the other end is tightened or loosened at will. The 
separate parts are enlarged one-fourth. 
