On conditions necessary to obtain a clean milk supply and on methods of testing cows' milk in relation to standards of cleanness : report to the Sub-committee on clean milk / by S. Delépine, June 16th, 1918.

  • Delépine, Sheridan, 1855-1921.
Date:
1918
Catalogue details

Licence: In copyright

Credit: On conditions necessary to obtain a clean milk supply and on methods of testing cows' milk in relation to standards of cleanness : report to the Sub-committee on clean milk / by S. Delépine, June 16th, 1918. Source: Wellcome Collection.

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    In addition to these cellular products, some extraneous or foreign matter is almost invariably present in cow’s milk as supplied by the farmer. When milking is carefully conducted and the milk properly handled the extraneous matter is very scanty, and consists chiefly of a few cow hairs, some epithelial scales derived from the epidermis, a few' vegetable or mineral particles derived from the dust in the air. But wdien the shippons, cows, and milkers are dirty, the milk carelessly handled, the dairy vessels and water supply not clean, the a,mount of extraneous matter and'the variety of its constituents increase consider¬ ably. Among the extraneous products I may mention, wool, cotton, and other fibres derived from the clothing of the milker, from strainers, and from other articles used in the dairy. Animal, vegetable, and mineral matter derived from food, water, litter, dung, soil, and all kinds of dirt adhering to the skin of the cow, the hands and clothing of the milker, etc. Various animalcules, moulds, algse, bacteria (derived from the fodder, litter, water, farm animals, and workers) may also find their wny into the milk. Micro-organisms of various kinds, including some capable of producing disease, may infect the milk in several w^ays. The object of the mechanical methods of examination is to discover w'hether milk contains more cellular and extraneous products than has been found to be the irreducible minimum under satisfactory circumstances. The following mechanical methods may be mentioned among others :— Filtration method.—A definite amount of milk is filtered through a piece of some white fabric such as flannel, flannelette, or other porous material, through which milk filters readily. The dirt causes a dis¬ colouration of the part of the filter through which the milk has passed. The degree of discolouration indicates roughly the amount of dirt present. By this method it is difficult to form an accurate idea of the amount of cellular products. More elaborate methods of filtration have been used by some observers. Slaw sedimentation methods.—^The simplest of these consists in allowing a fairly large amount of milk to stand for twelve or twenty-four hours in a tall cylindrical glass vessel. The amount and characters of the deposit which forms at the bottom of the vessel are then observed. There are objections to this method, viz. : its slowness and the large amount of milk w'hich some observers require for each test (nearly 1 quart). Some preservative has to be added to the milk to prevent the changes liable to occur during the long period the fluid has to remain under observation. Quick sedimentation method or centrifugalisation.—This is the method which I have used at the Public Health Laboratory during the past twenty- two years. The amount of milk used for a test w'as up to about twnlve years ago 40 cc. (about If ounces). Since then I have preferred to take 50 cc. (If ounces) for this test. - The quantity of milk used was in part deter-