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point of contact on its twelve to forty-eight hour journey to the consumer it receives additional bacteria.
Milk holds a peculiar position among foodstuffs in that it is an excellent medium for the growth of many micro-organisms, both the ordinary saprophytic varieties and those pathogenic to man. These factors often produce in market milk an enormous bacterial content. Zakharbekoff found that in St. Petersburg examination of samples of milk as delivered to the houses showed the presence of from 10,200,000 to 82,300,000 bacteria per cubic centimeter. Samples of market milk at Giessen have shown over 169,000,000 per cubic centimeter, New York City milk as high as 35,200,000, London milk 31,888,000. In Washington, examinations made at the Hygienic Laboratory of the Public Health and Marine Hospital Service during the summer of 1906 showed a maximum of 307,800,000 and an average bacterial content of 22,134,289. Were milk transparent, this luxuriant growth would be evident to the naked eye, but because of its opacity such contamination occurs unnoticed. Fortunately, most of these organisms are sa prophytes, but there are good reasons to believe that they may elaborate toxins, rendering milk dangerous as a food.
It is evident, from a broad view of the subject, that a pure and wholesome milk supply is possible, and this volume contains all the necessary information to attain that end, as well as the existing standards of purity to which it should conform.
The three cardinal requirements, cleanliness, cold, and speedy transportation from the cow to the consumer must be observed, and the cow herself must be free from disease. For their observance, intelligence and care on the part of the dairyman and milk dealer are absolutely essential.
The bearing of all these points upon the wholesomeness of milk, its treatment when contaminated, and its use as an article of food, especially for infants, has been treated in detail by the various collaborators. To ascertain how serious an indictment might be returned against milk as a carrier of disease, a compilation of epidemics produced by this means has been made by Doctor Trask. Reports of 500 epidemics have been abstracted in tabular form and appear in the text. These are only the few that have been reported and are accessible in the literature; how small a fraction of all cases this must be can only be surmised.
As a result of large experience, Doctor Lumsden describes how the milk supply of cities becomes contaminated with typhoid bacilli, and the best epidemiological methods of determining the influence of milk as a factor in the propagation of typhoid fever.
With a view to determining the presence or absence of tubercle bacilli in the market milk of Washington, Doctor Anderson examined
272 samples from 101 dairies. He found that 6.72 per cent of the samples contained tubercle bacilli virulent for guinea pigs, and that 11 per cent of the dairies whose milk was examined supplied milk containing these micro-organisms in sufficient number and virulence to render guinea pigs tuberculous. The milk purchased by one charitable institution for the use of children caused tuberculosis in the animals upon which it was tested.
Evidence of this character again emphasizes the necessity of applying the tuberculin test among dairy herds, and taking necessary precautions with respect to milk of doubtful character.
In a second paper Doctor Anderson summarizes the evidence proving that Malta fever may be spread by infected goat's milk.
A peculiar disease, known as “milk sickness," is described by Doctor McCoy. Although fortunately rare at the present time, cases continue to occur in the mountainous sections of Tennessee and elsewhere.
Doctor Stiles shows that so far as the zoo-parasitic diseases of man are concerned, there is little to fear concerning the presence of such parasites in milk.
Statistical studies of mortality and morbidity, as influenced by milk, have been made by Doctor Eager. He gives figures to prove that the high infantile mortality may be attributed almost entirely to impure milk.
Doctor Wiley discusses the subject of ice cream, its use as an article of food, its composition, the extent to which it may be contaminated or adulterated, and the result of such contamination upon the public health. He also refers to the established standards governing its manufacture, and presents evidence to show their reasonableness both to the manufacturer and consumer.
Doctors Kastle and Roberts give a general survey of our present knowledge regarding the physical and chemical characteristics of milk, as well as the chemical changes in milk brought about by the action of heat and acids; and also those changes accomplished by the action of enzymes and microorganisms. The subject of milk adulteration is also considered. It has been shown, as the result of original investigations, that the milk ferments can withstand a temperature of 60° to 65° C. for some time without material injury. Twelve per cent of the samples of Washington market milk examined were found to be below the legal standard, 3.7 per cent gave evidence of having been watered, and a very large proportion of the samples examined contained appreciable quantities of dirt. None of the samples examined contained artificial coloring matters, and only one contained milk preservatives.
Doctor Rosenau shows, as a result of many hundred bacteriologic examinations of the market milk of Washington made in the Hygienic Laboratory, that for the most part it is old, warm and dirty. In the summer of 1906 the market milk contained on an average of 22,134,289 bacteria per cubic centimeter, and was delivered at an average temperature of 16.5° C. During 1907 the average was 11,000,000 bacteria per cubic centimeter, and temperature 14.2° C. The advantages of bacterial counts to the health officer and to the practical dairyman are pointed out.
As a result of original investigations, Doctor Rosenau and Doctor McCoy demonstrate the causes of the phenomenon known as the germicidal property of milk. They show that the decrease in the number of bacteria in fresh milk is for the most part apparent, not real, and further that the restraining action of milk can not take the place of cleanliness and ice, but may be taken advantage of in good dairy methods.
Doctor Miller reviews the significance of leucocytes and streptococci in milk and points out the unsatisfactory state of our knowledge concerning their sanitary significance.
Doctor Mohler points out that probably the most important disease of cows from the standpoint of public health is tuberculosis, and that it is also the most prevalent. The German commission on tuberculosis found over 10 per cent (6 out of 56) cultures of tubercle bacilli of human origin, virulent for cattle. In a similar series of tests conducted by the British Royal Commission on tuberculosis, 60 cases of the disease in the human being were tested with the result that 14 were claimed by this commission to have been infected from bovine sources. It has been found by Schroeder in this country that even when tubercle bacilli are not being excreted by the udder the dirt and manure of the stables where the diseased animals are kept are in many cases contaminated with tubercle bacilli. This contaminated material may readily infect the milk even though it comes from a healthy cow. In a recent examination at the Bureau of Animal Industry, Experiment Station, of the manure passed by 12 cows purchased from dairy farms in this city and infected with tuberculosis to an extent only demonstrable by the tuberculin test, tubercle bacilli were found in over 41 per cent of the cases.
Mohler estimates that probably 25 per cent of all the cows which supply milk to the District of Columbia are tuberculosis. He further points out the great practical value of the tuberculin test and insists that all milk should come from either tuberculin tested cattle or be subjected to pasteurization under the supervision of the Health Department in case the herd is not tuberculin tested.
Mr. Webster, among other things, emphasizes the value of the score card in the sanitary inspection of dairies and its bearing on the production of clean milk. He also gives 21 very useful suggestions concerning the cows, stables, milk houses, and methods of milking and handling milk.
Doctor Bolton writes of the dangers from contaminated water supplies on dairy farms and shows that a pure water supply on the farm appears to present much fewer difficulties than the same problem in towns. Each supply presents its own problem which must be solved for itself, with proper recognition of the objects to be aimed at, and these are purity, abundance, and convenience.
Doctor Bolton also gives the methods and results of the examination of the water supply of dairies supplying the District of Columbia. The analysis of results seems to show that there are comparatively few water supplies on the dairy farms visited which are free from sanitary objection, but in spite of this fact it is nevertheless probable that in many or most cases the faults can be rectified with little expense.
Doctor Melvin offers a practical solution of the classification of market milk. He proposes three grades: (1) Certified milk; (2) inspected milk, and (3) pasteurized milk.
Doctor Kerr gives a brief outline of the organization and conduct of medical milk commissions in the United States, established to foster the production of “ certified milk.” Emphasis is laid on the fact that the plan was formulated by a physician, and that it contemplates the sanitary supervision of dairies by a commission appointed by the local medical society for the purpose of producing pure milk especially for the use of infants and invalids. In this paper are included copies of the first contract entered into between a medical milk commission and a dairyman; also the requirements of the milk commission of the medical society of the county of New York, which contain all of the essential rules required by other commissions for the production of pure milk.
It appears that this movement has been a potent factor in improving the character of the milk supply in various parts of the country. as it has required that only tuberculous-free cattle should be used for the production of milk, that their milk should be cooled to a temperature of 45° F. and transported in a manner so that it reaches the consumer before noticeable biological or chemical changes have occurred therein. He also refers to the founding of infants' milk depots in the United States, and presents in tabular form the number of such organizations and other pertinent information relating thereto. The important subject of pasteurization has been carefully studied
tor Rosenau, who points out its advantages and discusses its
inconveniences. He recommends 60° C. for twenty minutes as the best temperature to use in pasteurizing milk, as this degree of heat is sufficient to destroy the pathogenic micro-organisms without devitalizing the milk itself. While pasteurization is not the ideal to be sought, practically, it is forced upon us by present conditions. It prevents much sickness and saves many lives—facts which justify its use under proper conditions. It is recommended that in large communities at least, pasteurization should be under direct supervision of the health authorities.
The trend of our modern knowledge upon the important subject of infant feeding is stated in Doctor Schereschewsky's article on this subject. The importance of breast feeding is emphasized. It is shown that the caloric needs of the infant must be considered in order to insure success in artificial feeding. Some of the errors of formula feeding are pointed out, and stress is properly laid upon the disastrous results which frequently ensue from overfeeding, especially with excessive amounts of butter fat. Schereschewsky believes that there is no relation between the heating of milk and infantile scurvy, and shows how this disease may result from qualities in the milk, other than those resulting from heating.
In the last three articles named, as well as elsewhere in this bulletin, references will be observed to the achievements of Mr. Nathan Straus in promoting the use of clean pasteurized milk for infants and the establishment of infants' milk depots both in the United States and abroad, and it is proper here to give recognition to his philanthropic and successful efforts.
Doctor Woodward describes the municipal regulation of the milk supply of the District of Columbia. He recounts the history of the development of the milk inspection service which consists of supervision, inspection of dairies and dairy farms, and inspection of the milk. It is shown that these measures have resulted in the improvement of the milk supply, and that there has been a notable reduction of morbidity following their inauguration.
The laws and ordinances governing the supervision of milk are given, and in addition copies of the forms of reports, etc., which are of value to those having supervision of milk supplies.
Acknowledgments are here made to Doctor Woodward and the officers of the Bureaus of Animal Industry and Chemistry for their hearty cooperation and contributions upon this important subject.