Fig. 51.—Messrs. Hearson & Company's "Lactobator," showing the internal arrangements.
A copper vessel made to contain water has placed in it a stoneware jar which holds two gallons of milk; on the top is a lid which carries a thermometer for indicating the temperature of the milk. Heat is supplied by a gas ring under the copper vessel; and in the gas supply is the patent thermostat made use of by Messrs. Hearson also in their biological and poultry incubators, in which a capsule containing a liquid arranged to boil at a certain predetermined temperature is the regulating factor. When the liquid boils, the capsule expands, and by certain mechanical devices regulates the gas supply so as to produce exactly the temperature required.
The procedure is as follows: The jar is filled with milk, and water is run into the copper vessel by the funnel until it runs over at the overflow pipe. The thermostat is lifted off and the full gas supply allowed to pass to the burner, the temperature of the milk brought up to 180° F. and maintained for half an hour at this figure. The gas is then turned off, and cold water run through the funnel until the temperature of the milk registers 95° F. The culture is added, the lid replaced, and the thermostat put into the pocket at the side of the vessel; the gas relighted, and when the temperature reaches 100° to 106° F. the capsule of the thermostat will expand and close the gas to a peep, which is just sufficient to maintain the temperature within the above limits. After eight hours the incubation is completed.
Edgar's patent apparatus, the "Lactogenerator," as provided by the Dairy Supply Co., Ltd., is shown in Fig. 52.
Fig. 52. Edgar's "Lactogenerator"
The milk is placed in a tinned copper-jacketed vessel and water run in through a vertical pipe until it runs off at the overflow. Two gas connections are required with cocks on each, the one to heat up the milk to the boiling point and maintain it at this for thirty minutes. A skimmer which has been placed in the milk lifts out the coagulated protein and albumen which rise to the top. The cock is then shut and cold water run through the jacket till the thermometer shows 90° F., when the culture is added, and the other gas supply with the regulator turned on, and the temperature is automatically maintained at about 90° F. Time of incubation eight to nine hours. It is recommended to turn cold water into the jacket at the end of the period to prevent overincubation.
A somewhat similar apparatus is that of the Willows Refrigerating Co., Ltd. (Fig. 53), with the exception that it has no automatic heat regulator. It is made of tinned steel, and the operations are the same, but the sterilising temperature (obtained by a gas ring or hot plate) is given as 180°, and the incubating temperature 100° to 104° F. for a period of twelve hours. Presumably this temperature is maintained by a small gas jet or other similar source of heat. The capacity is two gallons.