62 



SCIENCE 



[N. S. Vol. XXXVI. No. 915 



together, they were fastened together with 

 bolts or rivets. This makes it impossible for 

 the parts to draw apart and thus greatly re- 

 duce the efficiency of the entire incubator. 



The greatest departure from the original 

 ■was made in the construction of the doors. 

 The large doors opening out on hinges at the 

 bottom seemed highly objectionable from the 

 standpoint of convenience for those who reg- 

 ularly make use of the apparatus. Instead of 

 providing each of the four main compart- 

 ments with two single doors, one set of double 

 doors was fitted to each division. These doors 

 are made of heavy copper sheeting, and are 

 two-walled. They are about three inches thick, 

 and are so constructed as to fit perfectly into 

 the fronts of the respective compartments, 

 and to come together in such a way as to 

 allow of no appreciable diffusion of heat. 

 They swing on hinges at the sides of the di- 

 visions. The hinges are firmly attached by a 

 special device. The doors are made to close 

 tightly by means of fasteners situated at the 

 tops and bottoms. Besides the single pair of 

 doors for each large division, each small com- 

 partment is provided with its own movable 

 glass door, as in the original model. The two- 

 walled thick outer door, which is filled with 

 air space, makes a third door unnecessary. 



The approximate dimensions of the incu- 

 bator are as follows : Length (outside meas- 

 urement), 8 feet and 9 inches; height (not 

 including ice box), 2 feet and 9 inches; width, 

 2 feet and 6 inches. Inside measurements of 

 individual compartments: Divisions in section 

 A, each 11 inches wide and 23 inches high; 

 separate compartments in sections B and C, 

 8 inches wide and 23 inches high; and the 

 inner receptacle or box in the refrigerator di- 

 vision, 23 inches cube. 



The incubator rests on a strong wooden 

 stand which is 30 inches high. At the re- 

 frigerator end there is a specially constructed 

 platform by means of which the ice carrier 

 has easy access to the ice box. To further 

 facilitate the replenishing of the ice supply, 

 the outer lid of the ice box has attached to it 

 a stout cord, to the further end of which a 

 heavy iron weight is fastened. The cord 



passes over a pulley which is fixed to the ceil- 

 ing of the room. 



The apparatus has been in operation for al- 

 most a year, and has proved highly satisfac- 

 tory. The temperatures in the different com- 

 partments have been practically constant, 

 even when there were marked fluctuations in 

 the temperature of the room. To obtain the 

 maximum efficiency, however, the thermo- 

 regulator must be in good working condition, 

 and the ice supply must be replenished at reg- 

 ular intervals. The incubator has been in 

 operation during the warmest summer season 

 as well as in the coldest winter months, with 

 but very slight variations in the inner tem- 

 peratures, except during a few days of last 

 summer when the temperature of the room 

 was far above blood heat. 



Aside from tests made by myself frequently, 

 a rather exhaustive investigation of the con- 

 stancy of the temperature of the different 

 compartments was made by certain members 

 of the Tale biological department in connec- 

 tion with their determination of the tempera- 

 ture coefficient of the rate of reproduction of 

 Paramecium aurelia.' The temperature in 

 each compartment was recorded by a tube 

 thermometer, a maximum and minimum reg- 

 istering thermometer, and in one chamber 

 also by a thermograph. In their report of the 

 investigation we find the following state- 

 ments. 



The temperatures of the various compartments 

 were not only kept practically constant, but, which 

 is more important from the standpoint of these 

 experiments, the very slight variations which oc- 

 curred, appeared practically the same in all the 

 compartments simultaneously. 



Leo F. Eettger 



Yale TJniveesity 



a convenient 20° incubator 

 An incubator that will work satisfactorily 

 with gelatin culture media during the hot 

 summer and in our usually superheated labo- 

 ratories in winter is a great desideratum. A 

 number of expensive devices of this character 



"WoodrufiE and Baitsell, American Journal of 

 Physiology, XXIX., 147-155, 1911. 



