508 



Milking Machines. 



[Sept., 



milk tubes, and the receiver. It is at all times difficult to free 

 these parts from the residual milk after the "milking operations, 

 and in summer, when the warm weather favours the multipli- 

 cation of bacteria, special difficulty is likely to be experienced 

 with machine-drawn milk. Cleansing or sterilising would be 

 a more simple matter if boiling water or steam could be passed 

 through the apparatus. While this can be done with the metal 

 parts, it is impracticable with the rubber linings and tubes, 

 which would quickly perish under such treatment. It is, there- 

 fore, necessary, in order to ensure cleanliness in production, for 

 each part of the machine to be detached and cleansed separately 

 in a particular way. 



Experiments have suggested that the best liquid for cleansing 

 the rubber parts is a solution of brine and chloride of lime; 

 10 lb. of common salt and J lb. of chloride of lime added to 

 7 gallons of water have been recommended. As this 

 solution deteriorates, chloride of lime should be added each 

 week. The procedure in cleansing is first to wash out the 

 machine by sucking clean water through it, followed by warm 

 soda water to get rid of any trace of milk and to prevent the 

 deposition of fat, and then by warm water to get rid of 

 the soda. Finally, the whole apparatus from the receiver to 

 the teat-cups should be taken apart; the receiver, "claw" 

 and metal parts of the cups cleansed or sterilised by steam or 

 boiling water ; and the rubber tubes and linings should be kept in 

 the brine and lime solution until the next milking, when they 

 should be rinsed before using. The salt bath has no injurious 

 action on the rubber, and in fact acts as a preservative. 



These operations naturally take time, but such cleansing is 

 necessary to ensure that the milk obtained shall be of good 

 quality. Provided that every care is taken in cleansing the 

 machine, and that cotton niters are used for the air reliefs in 

 those machines in which they exist, milk of a very high grade 

 may be obtained, comparable with that produced under the best 

 conditions by hand. 



Having given these directions, Dr. Orr offers a comforting 

 pendant to the gruesome picture with which he illustrated the 

 necessity of cleanliness. In 1906 Erf, in a series of 12 experi- 

 ments, found a bacterial content of 3,700 per cubic centimetre 

 in hand-drawn milk and 2,200 per cubic centimetre in machine- 

 drawn milk— both produced under the best conditions. Stocking 

 and Mason (1907), in a similar experiment, obtained the follow- 

 ing figures :— Hand-drawn, 4,560; machine-drawn. 1.578. 



