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(4) City consumers and city children learn how milk is produced and its importance in nutrition.

(5) Theater audiences see entertaining films with a nutrition moral.

A number of improvements in the machinery for projection as well as the film itself have made possible a wider use of dairy films in educational work during the past two years. Almost all of the fire risk is eliminated by the use of the so-called safety film and any one of a number of standard portable projectors using incandescent lamps. The brilliancy of the picture shown by such projectors has been increased by the use of a generator for electricity attachable to any automobile.

A number of limiting factors prevent much wider use of motion pictures in the dairy education field:

(1) The regular quick-burning film is not recommended for use without a fire-proof booth. This seriously restricts the number of films that are available to the user of a portable machine, as at present an overwhelming majority of all films are printed only on this inflammable stock. Also, slow-burning films at present are produced in a variety of widths without uniformity of sprocket holes. It is hoped that a concerted effort will be made by all interested agencies to have all films, certainly all educational films, printed only on the slow-burning or safety standard width (noninflammable) stock.

(2) State laws with reference to educational motion-picture exhibitions need immediate standardization, and in many cases intelligent amendment. The hand of a lobby of the commercial motionpicture interests fearing competition has been felt in many States, and some laws might indicate that it had helped dietate the policies that have prevailed. In many States, particularly in New England, the only film that can be used without a booth is a narrow-gauge one in which no motion pictures are produced except when specially ordered. New England, therefore, can not tap any large reservoir of desirable films. In some cities it is necessary to use an asbestos booth, even with noninflammable films, and safety fire-proof portable projectors. The Philadelphia Interstate Dairy Council operates in four States. There is no uniformity of regulation in the four States, or in the cities within them.

It is unnecessary to describe the motion pictures now available. Everyone interested can see them for himself. The theme and the composition of many of them compare favorably with those shown in any commercial theater. I trust everyone has had an opportunity of seeing them.

As a part of an educational meeting, either city or country, the motion picture has a distinct place. It is accurate and graphic in description, and in it facts are technically detailed and entertainingly presented. Appealing to the eye, the sense through which we are told we receive 87 per cent of our impressions, it most readily conveys the intended message, even to the dull and the uneducated.

Flexibility is given to many programs by the use of well-chosen films, which would not be possible to accomplish if the program were dependent wholly on addresses by qualified speakers. Movements, such as that of the hand in milking or in operating machines, can be thoroughly analyzed and explained by retarding the normal speed in reproduction in the motion pictures.

With a well-chosen story as a background, many nutrition and health themes, such as the value of milk to athletes and the care of milk in the home, can be told to immense groups, in the city moving. picture theaters. One United States Department of Agriculture picture, “Out of the Shadows," depicts the importance of bovine tuberculosis eradication so vividly that at a country meeting in Pennsylvania one night, a whole neighborhood was impressed with the danger of this disease and the importance of its elimination. One farmer walked into the farm bureau office the next morning, and said: “I wasn't ready before, but that picture last night was enough. When can I get my cows tested?”

The dairy council early recognized the value of motion pictures and uses them regularly in several fields.

The Philadelphia Interstate Dairy Council has produced two films, one of two reels (a half hour), and one of three reels (threequarters of an hour), to use in quality control work among milk producers and milk handlers. We consider this our most important field for motion pictures. These pictures have attracted large audiences in blacksmith shops, garages, country schoolhouses, grange halls, and churches. Many successful summer showings have been given in the open air. Comparative records show that the farmers and others present take home the lessons of these films, and in a very large measure apply them individually.

(3) The National Dairy Council has a larger group of films, some from the United States Department of Agriculture, some from other sources, and several of its own production, that are used regularly as one of the features of nutrition and civics meetings in our great consuming centers. These meetings are held in schoolhouses, community houses, churches, Young Men's Christian Association and Young Women's Christian Association halls, etc. Films are regularly borrowed by school departments to aid in the teaching of such topics as health, civics, and commercial geography.

(4) Carefully selected films are being very successfully distributed by the dairy councils in the theaters. The National Dairy Council has purchased some of these from other agencies, and two have been produced in Philadelphia by the Philadelphia Interstate Dairy Council. The first one of its own production, "Highland Lassie." was shown to 1,000,000 people in Philadelphia, Trenton, Camden. Chester, and in the seashore towns last winter. The last one released, “Shadows" is now fairly launched on a winter's campaign in a number of cities. (All dairy council films are being shown at the National Dairy Council booth on the grounds during the National Dairy Show.)

To avoid duplication of effort and to insure a uniform high standard of production, a national production committee should be established, or some existing organization, such as the National Dairy Council, should be designated to coordinate the production of dairy films. Many times lately it has been found that two different agencies had, unknown to each other. been working on the same theme, thus producing two pictures where one would have served the purpose.

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There are many films, needed now in a national way, which are not produced because no one agency has sufficient distribution in itself to absorb the heavy cost of production; also the production of films is a highly specialized calling and needs special experience and training

One hesitates, in so short a paper, to moralize on the value of the motion picture as a medium to be used in dairy education. That principle seems so self-evident as to be almost axiomatic. I have tried briefly to point out some of the ways that films are now successfully used, and to characterize some of the types of pictures available. I hope that I have not overemphasized the difficulties involved at the present time. By motion pictures, new developments in dairying are graphically portrayed to our own dairy interests and by them, also, we are keeping before the public those fundamental factors that make the dairy industry so absolutely essential to human welfare.

Chairman WELD. We all know the value of the research work that has been carried on. Mr. S. H. Ayers will now present a paper on the subject “What constitutes efficiency in Pasteurization." Mr. Avers is now the research director, Glass Container Association. I take pleasure in introducing Mr. Ayers.

WHAT CONSTITUTES EFFICIENCY IN PASTEURIZATION.

S. HENRY AYERS, research laboratories, Dairy Division, United States Depart

ment of Agriculture.

Before undertaking to discuss efficiency in Pasteurization, we must have a clear understanding of the object of the process.

Pasteurization as applied to milk for direct consumption was conceived as a public health measure. Its object was and still is to make milk safe for consumption by the destruction of any disease germs with which it may have become contaminated.

Milk may of course be heated properly and then contaminated after Pasteurizing, so the efficiency of Pasteurization must be based upon the success in carrying out a number of steps which really make up the process. Successful operation must be first viewed from the angle of the object of the process and not from a financial viewpoint.

I do not mean to imply that milk-plant economics are not to be taken into consideration in milk-plant operation, for these have much to do with successful operation. The thought I wish to convey is that the efficiency of Pasteurization, as a public health measure, is of primary importance, both to health authorities and milk dealers. and, as discussed in this paper, applies to the successful operation of the process as a means of making milk safe.

THE PASTEURIZING PROCESS.

For the process to be efficient it must be based on correct principles which, briefly outlined, are as follows:

1. Heat all the milk to 145° F., and hold all the milk for 30 minutes.

2. Handle milk during cooling, bottling, storage and delivery, so that no contamination by pathogenic organisms can occur.

Proper Pasteurization comprises two distinct phases. The first is concerned with heating milk so as to destroy any pathogenic organisms in the raw milk, and the second has to do with proper handling to prevent reinfection with disease germs.

BACTERIA AS A MEASURE OF EFFICIENCY.

Bacteria counts and special tests are used as an indication of the efficiency of Pasteurization, so that it seems advisable to discuss rather fully the application and limitations of these tests.

In discussing bacteria counts I am considering the official count made on standard agar incubated for 48 hours at 37° C. It must be stated, however, that neither this medium nor temperature gives the full value which may be obtained by plating methods. If we are to make progress along the line of bacteria control we must have qualitative as well as quantitative results.

The use of milk powder agar, devised in our laboratories, which gives qualitative results, seems to be a step in the right direction. There is, however, a decided sentiment against the use of this medium because it gives higher counts than standard agar, and health officials feel that its use would necessitate changing bacteria standards. But if progress is to be made the view of these officials must change with new developments..

It should be kept in mind that the discussions of bacteria counts in this paper are confined to the present official methods.

RAW MILK.

If there were quick means for detecting pathogenic organisms in milk, then bacteria tests would provide a direct and simple measure of efficiency, but, unfortunately, such methods are not available. It therefore becomes necessary to rely upon bacteria counts, properly made and interpreted, as a general index of conditions or upon tests for specific types of bacteria. A low count, either in raw or Pasteurized milk, does not guarantee the absence of disease germs. The epidemic of typhoid fever at Fort McPherson, Ga., traced to a raw-milk supply with a bacteria count which averaged from 2,000 to 5,000 per cubic centimeter offers striking proof of this fact. However, bacteria counts in raw milk bear a somewhat direct relation to conditions of production and handling

While a low count with raw milk does not guarantee freedom from disease germs, it does indicate care in production and handling, and with a lessening of contamination and increased care in handling, there must be a decreasing chance of infection with pathogenic organisms.

PASTEURIZED MILK.

The bacteria count of Pasteurized milk is more complicated when it comes to interpretation, and bears only a general relation to the count before Pasteurization. Generally speaking, a highcount raw milk will give a high-count Pasteurized milk, but there are so many complicating factors that this can not be observed as a strict rule.

The interpretation of a bacteria count of any milk, whether raw or Pasteurized, can at best only serve as a general index and should be used with this idea in mind. When made under definite conditions with a definite medium and the same methods, counts provide a picture of a combination of conditions with regard to milk which, if interpreted correctly, give an idea of any important changes in these conditions. Such information provided by routine tests should serve to point out unusual changes which require further investigation.

When used in this manner routine bacteria counts made by the laboratories of health departments and milk dealers are valuable, but it is nothing short of ridiculous to depend upon bacteria counts of Pasteurized milk as the only means of determining efficiency and as a measure of safe milk.

In order to interpret the count properly, consideration must be first given as to where and when the sample was taken. If the sample represents fresh Pasteurized milk, and is taken at the plant immediately after bottling, the count measures the numbers of bacteria which survive the heating process, together with any contamination through machinery and bottles. If taken from delivery wagons, the count will measure the same thing, but also, in addition, any growth which may have taken place.

When the counts are high in fresh-bottle Pasteurized milk, they may be due to contamination, to high-count raw milk, to an unusually high proportion of resistant types, or, in special cases, to growth of a thermophilic organism which will be discussed later.

In order to determine which of these causes is responsible, further investigation is required in which a series of samples are taken at each step in the process. The interpretation of the results of such a series is again complicated, because of the fact that there is no assurance that the samples represent the same milk at each step in the process. In some plants, it is, of course, possible to take samples in such a way that some of the same milk can be examined at various stages in Pasteurization. In other plants there is a continuous flow of milk, so varying in kinds and numbers of bacteria as to complicate seriously proper sampling. I am emphasizing some of these points so that there may be no false illusion that series samples on test runs can be analyzed and interpreted in a haphazard manner.

BACTERIA WHICH SURVIVE PASTEURIZATION.

It is impossible to interpret properly bacteria counts of Pasteurized milk or the results of special tests without a fundamental understanding of the bacteria which survive the process.

The bacteria flora of milk is extremely variable. Relatively speaking, it contains a few spore-forming bacteria which are resistant to Pasteurization. The majority of the bacteria are nonspore formers which were formerly thought to be destroyed by Pasteurization. Among these bacteria were included the lactic acid streptococci, which were believed to be destroyed.

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