INCUBATION OF CULTURES 



21 



Fig. II. 



metal tray containing a small quantity of water, and put in the 

 middle of the floor, and away from any inflammable materials. 

 This will be found to answer admirably, and 

 can easily be fitted up in an emergency. 



It would be better to use a tin box specially 

 made for the purpose, and having a door at 

 the side and a perforated false bottom, so 

 that the culture-tubes do not rest directly on 

 the metal exposed to the flame. This latter 

 had best be made of copper. 



Dr. Bottomley, of Boscombe, informs me 

 that he has used the simple apparatus shown 

 in Fig. 1 1 for five years, and finds it answers 

 admirably in the diagnosis of diphtheria, etc. 

 It is an ordinary square vaseline tin, into the 

 round opening of which is put a cylindrical 

 coffee tin. The outer tin is filled with water, 

 and a thermometer is put into a hole through its lid. The culture- 

 tubes are placed in the inner tin, and the apparatus is heated by a 

 paraffin lamp. 



If the practitioner is fortunate enough to possess a conservatory 

 which is kept at a temperature approximating to that of the body, 

 this will serve admirably. The culture-tubes must be kept in a 

 box which will exclude light. 



In the absence of this a cupboard near the kitchen fire or the 

 hot-water cistern may be found that will answer the purpose ; a 

 thermometer should be placed in it, and examined from time to 

 time throughout the day, and if the temperature does not fall 

 below 30° nor rise above 40°, it will serve at a pinch, though a 

 temperature which is more constant near 37° is desirable. It has 

 to be remembered that we are not now speaking of the incubation 

 of cultures for purposes of research ; we are dealing with methods 

 of cultivation which are necessary for diagnostic purposes, and 

 for these it is usually sufficient if the temperature remains nearly 

 constant at the proper point for some eighteen hours. 



Another method I have recently adopted is to use a " Thermos " 

 flask, or, what comes to the same thing, a Dewar's liquid air 

 flask. This is nearly filled with water at a temperature of about 

 40° C, and the culture-tube inserted. If a Thermos is used the 

 cap is then applied, if a Dewar's flask a few drops of oil are 

 placed on the surface of the water (to prevent evaporation, which 



