The experiment conducted under the direction of Doctor Pennington follows:

While the temperature of 0° C. is ordinarily accepted as that at which bacterial life is either quiescent or annihilated, the making of ice cream in a freezing mixture of ice and salt reduces the substances to a temperature of from -10° C. to -20° C. To test the action of this temperature on the very rich bacterial flora ordinarily occuring in commercial ice creams, samples were obtained from various sources and maintained for several days at a temperature varying at from -10° C. to −20° C. It has been found by inquiry and observation that ice cream may be kept by a manufactory or more likely by the retail dealer for a week or ten days. It is of course kept for greater lengths of time when provisioning ocean liners or stored for some particular purpose, but this is rather the exception. It was deemed advisable, therefore, to limit this preliminary investigation to the period which is ordinarily that of commerce.

The samples of ice cream tested were purchased in open market or sent directly from the manufacturer, who had no knowledge of the purpose for which they were intended. When coming from the manufacturer they were packed in the usual tin ice-cream storage can, set in an ice and salt mixture. When purchased from restaurants, confectioners, etc., the sample was obtained in a sterile wide-mouthed glass jar, tightly capped, and was immediately packed down in ice and salt. All the samples to facilitate keeping were placed in a room in the cold-storage warehouse, where the temperature was slightly below freezing. Here they were inspected daily, ice and salt added as required, and samples for study removed with sterile glass spatulas.

For the determination of the total number of organisms, approximately 1 cubic centimeter of the cream, which was melted as promptly as possible after reaching the laboratory, was weighed in a tared, sterile weighing bottle, made up to 10 cubic centimeters with sterile water, and from this mixture were prepared appropriate dilutions for the counting of organisms.

The plating was done on litmus lactose agar, half the plates of each sample being allowed to develop colonies at a temperature of 37° C., and the other half placed in the refrigerator, running from 18° C. to 20° C. It has been found necessary to use both these temperatures if an accurate idea is to be obtained of the changes undergone by organisms when submitted to continuous low temperatures, since there is apparently a dying off of certain groups of organisms in the early stages of storage, and the gradual increase of other organisms, which seem ultimately to thrive under what are usually conditions fatal to growth.

The results obtained in the study of 8 samples of ice cream are tabulated as Series I, II, and III, of Table I. Series I extended over sixty-six hours; Seres II covered a total of one hundred and ninety-two hours, and Series III a total of two hundred and sixteen hours.

As with all experiments where the bacterial flora is of as varied a character as that found in commercial cream, there is observed in this work a considcrable variation in the behavior of different samples. Generally the tendency is to show a decrease for at least several days in a number of organisms developing at body heat, though occasionally these organisms persist and thrive at low temperatures. The organisms developing at the temperature of the refrigerator show usually a period of decrease which may last several days, to be followed later by a very pronounced rise. Sometimes the killing off of the organisms is very slight, their numbers remaining almost stationary or making a continuous upward curve.

The experiments cited are too few to permit of formulating definite conclusions and it must not be forgotten that, purchased as they were-in open market-their histories unknown, there may have occurred a considerable part of the bacteriological cycle before the specimens were investigated. The results given simply show what may happen to commercial ice cream if kept for from three to ten days.

Two experiments have been made to test the action of freezing and thawing. For this work cream was obtained from a milk dealer, sweetened and flavored with vanilla in the laboratory, and frozen in a small hand freezer, which had been cleansed simply with hot water. After freezing the product was packed down in an ice-salt mixture and allowed to stand until the cream had thoroughly melted, though the temperature was still considerably below that of the surrounding atmosphere. It was then refrozen and again allowed to stand for

some hours.

At each step the bacterial count was made and recorded, as seen in Table II. Experiments of this character are of interest, not only for the tracing of decrease in numbers, but also as a possible source of information regarding the many cases of ice-cream poisoning blamed upon stale ice cream, and particularly that which had been melted and refrozen.

TABLE I.-Growth of bacteria in ice cream at the temperature of ice and salt ( —21° C. —— 5.8° F.).

TABLE II.-Bacterial growth in 'ce cream thawed and refrozen.

All of the samples which have been studied for cold storage history were examined also for the presence of streptococci. The results are indicated in the following list:

Eighty-two and five-tenths per cent showed the presence of the organism.

The method for the detection of streptococci in ice cream was as follows: The melted sample was centrifuged for half an hour in a Stewart lactocrite driven by a small motor of such power that the speed was approximately 3,000 revolutions per minute. This apparatus, which consists of a flat aluminum pan holding 20 tubes of 1 cubic centimeter capacity and stoppered at the outer end with a specially constructed rubber plug, causes the sediment not only to be thrown to the end of the tube but drives it against the rubber plug with such force it is almost quantitatively adherent to the plug. Accordingly, if one carefully removes the rubber stopper and by rubbing on a glass slide and over an area of known surface attaches the sediment, one can obtain, on staining and examining the film microscopically, an approximation of the number of organisms and leucocytes in 1 cubic centimeter of the liquid.

Because of the débris in ice cream, which ordinarily renders the usual method of centrifuging milk and cream samples quite impracticable, the above method was resorted to and, so far as the detection of the presence of streptococci was concerned, it was found eminently satisfactory.

THE SIGNIFICANCE OF A PURE ICE CREAM SUPPLY IN RELATION TO PUBLIC HEALTH.

A study of the literature dealing with diseases traced to the eating of ice cream shows that not only are isolated cases more or less severe, even sometimes resulting in death, fairly numerous, but widespread epidemics have been caused by the toxicity of the substance. Such diseases are, of course, of gastro-intestinal origin. Among these epidemics is one of typhoid fever described by Dr. George Turner, occurring at Depford in 1891, which was apparently caused by ice cream.

Another epidemic of this disease occurred in Liverpool in 1897 to which 27 cases were traced.

In 1902, in the city of London, 18 cases of typhoid fever were traced by the health officer of Finsbury (see report of health of Finsbury, 1902, page 67) to ice cream as the source of infection.

More commonly, however, the illness caused by ice cream has the symptoms of colic, headache, diarrhea, and depression rather than a specific typhoid infection. "Such an outbreak occurred in Birmingham during the summer of 1905 (Thresh & Porter, Preservatives in Foods and Food Examination, page 280) and was investigated by Dr. Robertson, the city medical officer of health. Out of 250 consumers served 52 cases of illness occurred, 4 only of the patients being over 14 years of age. The interval which elapsed between the eating of the ice cream and the onset of the illness varied from half an hour to eight and a half hours. All the persons suffered from diarrhea and collapse. No irritant poison was discoverable by chemical analysis. Professor Leith examined the ice cream bacteriologically and found therein a bacillus of the colon group capable of causing the death of guinea pigs. From an examination of the premises in which the ice cream was manufactured it appeared probable that it had become contaminated while standing in the cooling shed after boiling and before freezing. Opposite this shed there were 3 waterclosets in an extremely filthy condition, and possibly organisms of excremental origin had fallen upon one of the buckets of the cream while it was in a warm condition. These would rapidly multiply and may have produced toxins or ptomaines. Neither the bacilli nor their poisonous products would be affected by the subsequent freezing."

In the discussion of ice cream in "Bacteriology and Public Health," by George Newman, he states that a "small outbreak occurred in the city of London, affecting 16 telegraph boys. The symptoms were colic and diffuse abdominal pains, headache, vomiting, diarrhea, and nervous depression. Dr. Collingridge's inquiry resulted in the following conclusions:

(1) That in a number of cases of illness occurring among young persons of a susceptible age the symptoms were strictly identical and were characteristic of poisoning by ingestion of toxic material.

(2) That the cases reported followed the ingestion of ice creams.

(3) That ice creams subsequently obtained at shops frequented by the patients contained bacilli of a virulent character.

(4) That the symptoms observed were those generally following the ingestion of material containing such bacilli.

(5) That where pathogenic bacilli were found, the ices had been manufactured under insanitary conditions. The majority of the manufacturers are aliens, and although the premises may be kept in a fairly sanitary condition, their personal habits unfortunately leave much to be desired where the preparation of food is concerned."

Dr. Klein examined 24 samples of ice cream from the same locality and found 13, or 54 per cent, to be poisonous to guinea pigs.

In July of 1904 the medical officer of health of Battersea (Report of 1904, Public Health Committee of the London County Council) reported an outbreak of illness among the people who had eaten ice cream purchased at a particular shop. As usual in such toxemias the symptoms included abdominal pain, diarrhea, and collapse. The ice cream causing these poisonings had all been eaten and therefore could not be examined, but an inspection of the premises showed very filthy conditions and in all probability the contamination of the cream was due to a dust bin in the immediate proximity of the shelf on which the ice-cream vessels were stored.

Owing to outbreaks of this nature the London County Council (general powers act, 1902, secs. 42-45) has given powers for controlling this trade:

(a) Ice cream must be made and stored in sanitary premises.

(b) It must not be made or stored in living rooms.

(c) Strict precautions must be taken as to protection from contamination.

(d) Cases of infectious disease must be reported.

(e) The name and address of the maker must appear on street barrows.

These regulations are new for London, though they have practically been in existence in Glasgow since 1905, and in Liverpool since 1898.

That such powers are enforced by the officials having the public health of London in charge is demonstrated by the report, for example, of the sanitary conditions relating to the city of Westminster