APPARATUS FOR HEATING CULTURES TO SEPARATE 
SPORE-BEARING MICRO-ORGANISMS* 
By C. BALFOUR STEWART, M.A., M.B. Camb., Assistant Bacteriologist to the 
Liverpool Corporation 
Those who have occasion to work with spore- 
bearing micro-organisms must often have felt the want of 
an apparatus which would keep at a constant temperature 
of between 70° C. and 8o° C. 
An application of Meyer's hot air bath, such as is 
used in chemical laboratories, suggested itself as being 
most applicable to the purpose ; several of these were 
made and are now kept in every-day use in this labora- 
tory. They maintain a constant temperature of 80° C. 
without any attention, and are always ready for placing 
tube cultures in, and, what is more important, the cultures 
may be left without any fear of their becoming heated 
above 8o° C. 
The apparatus is similar in construction to 
Meyer's hot air bath, except that it is larger than those 
generally used and has no outlet from the bottom of the 
inner chamber. 
The inner chamber is 18 cm. deep and 9 cm. in 
diameter, and will take 7 or 8 tubes ; it is advisable to 
have a condensation tube of 1 m. in height. 
In use. — A small quantity of pure bensole BP 8o° C. is poured into the outer 
jacket through the hole for the condensation tube, and the tube is re-inserted. A small 
flame below will keep the bensole boiling, and as the vapour condenses in the 
condensation tube and runs back very little is lost. 
The inner chamber is filled to about one-third of its depth with water at 
8o° C. ; the water retains its heat when the lid is removed and acts as a good conductor 
of heat to the culture tubes when they are placed in it. If water is not put in 
the inner chamber the heated air escapes when the lid is removed and it takes a long 
From Centralhlatt f. Bakteriologie, xxvii Bakt, 1900, No. IO-II. 
