11. If the milk hygienic rules above mentioned are carefully followed, and if attention is paid to the experiences regarding a rational method of feeding milch cows, it is possible, without any further method of preserving the milk, to have the same capable of being transported and kept for sixteen hours without losing its adaptability as infant food. In Berlin I saw such a milk reach the consumer with a germ-content of not over 1000 germs per cubic centimeter. On the other hand, I have seen milk derived from dirty cows and collected without particular hygienic precautions, after being transported six hours, contain a hundred to a thousand times as many germs. In such cases, soon after milking, the milk often contains from 30,000 to 100,000 germs per cubic centimeter.
In the strictly fresh milk from my own cows the number of germs per cubic centimeter varies from 10 to 50 to 200. Such milk kept at room temperature does not coagulate until after three to five days.
At present I regard 1000 germs per cubic centimeter at the time of feeding to be a safe limit for milk fed to infants.
12. If a milk collected in accordance with the preceding regulations is to be made capable of being transported and kept for three days (in which case coagulation factors must be reckoned with) without losing its qualifications as an infant food, the addition of formaldehyde in the proportion of 1:40,000 (B. f. milk) is to be recommended.
The following manipulations are then to be carried out:
I. Preparing a formaldehyde stock solution containing 0.5% formaldehyde. (One part of commercial formaldehyde and 79 parts of boiled water.) This solution will keep for two or three days.
II. Pouring 50 c.c. of this 0.5% stock solution (= .25 gramme formaldehyde) into an empty tin pail in which a mark has been made at the 10-liter level.
III. Milking into this pail up to the mark.
IV. Straining, airing, cooling, etc., according to paragraph 10, IV, V, and VI.
13. In order not to conflict with the government sanitary regulations the milk producers at present delivering this B. f. milk have agreed to supply it only to certain private institutions designated by me.