148 AGRICULTURAL BACTERIOLOGY 



will suffice to keep the tubes in good condition. The action 

 of the solution must be supplemented by a thorough clean- 

 ing of the parts each week. As the tubes are used, minute 

 cracks form on the inner surface and become filled with 

 milk. The antiseptic solution enters them slowly, and the 

 bacterial growth that may occur therein will be forced out 

 of the cracks under the influence of the constantly chang- 

 ing pressure in the tubes when the machine is in use. 



The tubes may also be kept in a satisfactory sanitary 

 condition by placing them in water and heating to 176 F. 

 for a -few minutes. The tubes may be allowed to remain in 

 the water until they are to be used again. 



Cleaning of milk utensils. Milk utensils shoul<i be 

 washed as soon as possible after using, for if the milk is 

 allowed to dry on the surface of the utensils it is difficult 

 to remove. They should be rinsed with cold water, then 

 washed with a hot solution of a washing powder. Soaps 

 and soap powders are difficult to remove by rinsing, and are 

 not as effective in the removal of milk and grease as are 

 washing powders. A stiff brush should be used for scrub- 

 bing, for much of the dirt can be removed only by me- 

 chanical force. Finally, the vessel should be rinsed with 

 boiling water, using it in such quantities that the vessel will 

 be heated sufficiently, so that rapid and complete drying 

 will take place. The growth of microorganisms can not 

 occur in the absence of water. Imperfect washing will not 

 be so serious, if the utensil is perfectly dried, as will a more 

 thorough washing with imperfect drying. If steam is 

 available, the utensils can be so thoroughly heated as to 

 destroy all organisms that are likely to injure the keeping 

 quality of the milk. Furthermore, steaming facilitates the 

 drying process. In the washing-rooms of city milk depots, 

 can driers form an important part of the equipment. The 

 amount of bacterial growth that can take place in a few 



