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act of food assimilation that they will not be excreted through the mammary organs. We may therefore safely assume that all milk as produced by the dairy cow is free from contamination with typhoid bacilli; nevertheless, some of these organisms may gain entrance to it before it leaves the farm, while in transit to the market, at the distributing point, while being delivered at the homes of the consumers, or within these homes while being kept until needed for any of its usual varied domestic uses. Contamination may occur at any of these places through pouring the milk into vessels that have been soiled with typhoid infection, either directly with discharges from a typhoid-fever patient, or indirectly through infected wash water; by the entrance of germ-bearing flies to the can or bottle in which it is being stored; or by being handled by people who are themselves suffering from the disease in a mild form or who are caring for typhoid-fever patients. When we consider the small number of bacilli required to furnish the nucleus for a thrifty colony in a can of milk, and the great rapidity with which they multiply and pass through the fluid from one part of the can to another, we can only wonder that the infection of milk occurs as infrequently as it does. The house fly is recognized as a dangerous conveyer of infectious material, and if permitted to do so, there is no place to which he more readily carries typhoid infection, should he become smeared with it, than into a milk pan or a cream vat. It is not an uncommon occurrence at certain seasons of the year for flies to fall into the family milk supply, or into the cans or vats at the creamery. Such accidents are most frequent at a time of year in which typhoid fever is usually quite frequent-that is, in the late summer and fall. Ordinarily these struggling flies are harmless to the consumer of the milk in which they fall, whether they crawl out or drown. It is only in the exceptional cases of their contamination with some infectious disease that serious results may follow.
Since the typhoid organism thrives so well in milk, the question very naturally arises, What dangers are presented to humanity by the various dairy products through the possibility of their harboring typhoid bacilli, possibly for a period of months, and later conveying them to the digestive tracts of the consumers?
EXPERIMENTS TO DETERMINE THE PERSISTENCE OF TYPHOID BACILLI IN MILK AND BUTTER.
Typhoid bacilli in milk or butter will live and retain their active virulent properties for weeks and even months. In order to determine the length of this endurance when the infected dairy products are kept under common market conditions, the Pathological Division of the Bureau of Animal Industry recently prepared some samples of milk and butter purposely infected with typhoid bacilli and kept
them in an ice chest at the laboratory, where they were easily available for daily examination.
PERSISTENCE IN BUTTER.
The butter was prepared by adding a quantity of typhoid culture, scraped from a thrifty growth upon glycerin agar, to the cream from which the butter was to be made just before it was placed in the churn for churning. After the churning the buttermilk was worked out, salt in the usual proportions was added, and the finished product was then packed securely in small glass jars which were kept in cold storage until the completion of the investigation.
Tests of this butter were made by plating every two or three days following its manufacture, as by this process the presence of living typhoid bacilli could readily be demonstrated. Each day that a test was made a bouillon culture tube and two agar plates were prepared. The preparations made on certain days would occasionally prove sterile. This was probably due to the fact that the needle with which the sample was removed from the bulk of butter in the jar passed into a portion of the mass in which no typhoid bacilli happened to be left at the final working and packing. This supposition seemed warranted by the fact that plates made from other portions of the same jar on the following day frequently developed good colonies of typhoid bacilli. The tests were continued until negative results had been obtained with eight consecutive platings, extending over a period of fifteen days.
Living colonies of typhoid bacilli developed in plates that were made from butter made and stored as described above on the one hundred and fifty-first day after its manufacture. This proves that typhoid bacilli will retain their vitality under these conditions for one hundred and fifty-one days, and that during this period these microorganisms are ready to multiply whenever they are placed in suitable environment. Suitable conditions may be furnished by the system of some person who during this time unknowingly eats infected butter supposing it to be wholesome.
PERSISTENCE IN MILK.
The length of time that typhoid bacilli will remain active under common market conditions in milk far exceeds the period during which it is ordinarily kept before being put to some sort of domestic use. We have taken tubes of culture milk, inoculated them with typhoid bacilli, incubated them at body temperature over night, and then found on examination under the microscope that the fluid was fairly swarming with actively moving bacilli. These samples of infected milk were then placed in the laboratory ice chest for storage.
Examination, repeated at intervals of three or four days, showed that the organisms retained active motility for some twenty days, and the number of organisms present in each drop at the time of its examination had apparently suffered no diminution up to this point. Later than this there was a gradual lessening in the number present and their motions were less active until, on the forty-third day, they had practically disappeared. Sterilization of the cream previous to its being churned is therefore indicated in all cases in which there is any possibility of typhoid infection.
ADVANTAGES OF PASTEURIZING MILK AND CREAM.
It has been found by means of numerous experiments that milk may be subjected to heat in such a manner and for such a length of time that all of the pathogenic bacteria which it may contain will be rendered harmless, and yet no alteration of the character or digestibility of the milk will result. The application of a temperature of 60° C. (or 140° F.) for twenty minutes will deprive typhoid bacilli and also the specific organisms of diphtheria, dysentery, cholera, and tuberculosis of all their harmful powers, and the pasteurization of milk or cream under these requirements will result in food products that are perfectly safe and that retain at the same time all of their original nutrient properties.
Whenever untraceable outbreaks of typhoid fever occur it might be well, while searching for a possible source, to bear in mind the fact that dairy products offer satisfactory shelter and nutriment to typhoid bacilli whenever they come in contact with them, and an investigation of the milk and butter supplies of the several affected families should therefore be made.
THE ACTION OF SALTPETER UPON THE COLOR OF MEAT.
By RALPH HOAGLAND,
In charge of Chicago Laboratory, Biochemic Division.
The importance of the meat-curing industry of the United States is apparent to anyone who considers that by far the larger portion of the hogs butchered is sold, not as fresh pork, but as cured or salt meat in the form of hams, bacon, mess pork, dry-salt meat, etc. There is also a large amount of pork cured by farmers for home consumption which is not generally considered in an estimate of our meat production. A considerable amount of beef is also pickled to be sold as corned beef, either canned or in bulk, or it is smoked and sold as dried beef.
The process of curing meat in practice at the large meat-packing establishments is, in general, the same in each one. The substances allowed by the regulations of the Secretary of Agriculture to be used in the curing of meat which is to enter interstate commerce are salt, sugar, saltpeter, spices, vinegar, and wood smoke. Pork is cured either by the dry process, in which a mixture of salt, saltpeter, and sugar is rubbed into the meat, or by pickling the meat in a brine containing these ingredients. By far the larger amount of pork is cured in pickle. A similar pickle is commonly used in curing beef.
Practically all farmers who cure their own pork add a little saltpeter to the brine, and there is probably not a packing house in this country which does not use saltpeter in the curing of meats as well as in the manufacture of many brands of sausage.
Saltpeter is used in the curing of meats for two reasons: (1) It has a very decided preservative action when properly used-preventing the souring of meat; and (2) it acts upon the meat so as to preserve its natural color, or, more properly speaking, it gives to the cured meat an attractive color which is in some cases brighter than the natural color. Since borax and boric acid are not permitted in the curing of meats for interstate commerce, saltpeter is very highly prized by the packers on account of its preservative action. The question of whether or not saltpeter is harmful to health is not dealt.
with in this paper, the purpose being to treat only of its action upon the coloring matter of meat.
The action of saltpeter upon the color of meat is very apparent to anyone who has observed the bright-red color of corned beef which has been cured in pickle containing saltpeter. The same bright color may be noticed in a slice of smoked ham, in the lean meat of bacon. and especially in the case of summer sausage, in which saltpeter plays a very important part in the production of color.
REVIEW OF SOME PREVIOUS PUBLICATIONS.
In view of the importance of our meat-curing industry, it is surprising that in this country practically no attention from a scientific standpoint has been given to the changes which take place in meats during the process of curing. The action of saltpeter upon the coloring matter of meat has been given considerable attention by European investigators, but the results obtained have not been entirely in accord.
Mitchell in his handbook on flesh foods discusses the action of saltpeter upon the coloring matter of flesh, and quotes experiments by Weller and Riegel. These investigators obtained a bright-red ether extract from sausage prepared with saltpeter, and concluded that the color was due to the action of the saltpeter upon the coloring matter of the meat. The hemoglobin was found to have undergone alteration and to give a spectrum resembling methemoglobin. On treating hog's flesh containing blood with saltpeter they were able to obtain a colored extract with ether, but, on the other hand, were unable to obtain the color from flesh not containing blood.
E. Spaeth, also quoted by Mitchell, was unable to confirm the results obtained by Weller and Riegel relative to the action of saltpeter upon hog's blood.
Ostertag notes Weller and Riegel's experiments and also quotes Glage to the effect that the persistence of the red color of salt meat is not due to the saltpeter, but to nitrites, and perhaps nitric oxid, which are formed from the saltpeter in the brine.
Haldane in an article entitled "The red color of salted meat" treats quite fully of the action of saltpeter as a flesh-color preservative. As the result of his investigations he reaches the following conclusions:
1. The red color of cooked salt meat is due to the presence of NO hemochromogen.
2. The NO hemochromogen is produced by the decomposition by heat of NO hemoglobin, to which the red color of unsalted (?) meat is due.
a Figures refer to bibliography at end of article.
The term "unsalted" as it appears here is evidently a misprint, as the body of the paper clearly shows that uncooked salted meat is referred to.