TIME SAVING BACTERIOLOGICAL APPARATUS 5G1 



APPARATUS FOR STERILIZING WITH HOT AIR 



This apparatus is a large gas oven, known as the hotel size 

 oven, because such ovens are used extensively in hotel kitchens. 

 Figure 2 shows its general appearance. The oven is made of 

 non-rustable metal and is constructed on the principle of the 

 fireless cooker, being well insulated and the flame not entering 

 the chambers. 



Its main virtues are, first, its size — about 2500 petri dishes 

 can be sterilized at one time; second, case of sterilization — being 

 well insulated, the oven is heated to a certain temperature and 

 the gas is then turned off; third, the uniformity of sterilization- 

 all parts of the oven are evenly heated. The oven has given 

 great satisfaction. 



APPARATUS FOR CLARIFYING MEDIA 



Filtration of agar and gelatin has always been a time consum- 

 ing and unsatisfactory procedure. This is evidenced by the 

 many different methods which have been described in the litera- 

 ture and by the detailed instructions given in the methods for 

 preparing these media. The Laboratory Super-Centrifuge, 2 

 figure 3, makes it possible to secure clear media without the use 

 of egg albumin and without the trouble of filtering through cotton 

 or paper. With the trunnion kettle and the super-centrifuge, 

 the preparation of a large quantity of media becomes a simple 

 operation. A concrete example may be cited. It took one and 

 one-half hours to prepare, cook, and clarify 25 liters of agar, 

 ready for tubing. With 25 liters of agar there is a loss due to 

 clarifying of not over 500 cc. 



These Super-Centrifuge machines may be driven by compressed 

 air or by high pressure steam. Ours is attached to both systems, 

 but we find that the compressed air is more satisfactory for our 

 purpose. A speed of 30,000 revolutions per minute gives a 

 satisfactory filtrate. Equally satisfactory results are secured 



2 This illustration was kindly supplied by the Sharpies Company of West 

 Chester, Pennsylvania. 



