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Table VII.-Number of children included in the study, total possible number of days of
school attendance, and days absent on account of sickness and of causes other than sick-
Total possible days of
school attendance.... 669,214 54, 020 55, S60 57, 120 58, 400 66,700 72, 160 107,785 110, 269 86, 920
196 280 339 381 435 634 901 811 489
TABLE VIII.- Number of days lost from school on account of sickness of known cause
and number of cases of known discases among school children 6 to 18 ycars of age, in
TABLE IX.- Number of days lost from school on account of sickness of known cause
Data given here are for only the small part of the total absence from sickness in which the specific dis-
The following method for determining the phenol coefficient of
No single method can serve as a means of comparing the value in
This method was submitted to several different laboratories for trial before its adoption, and the results seem to justify the belief that the personal equation in the performance of the tests does not play an inordinate rôle.
THE TEST CULTURE.
The test culture is a culture of Bacillus typhosus, Hopkins strain. Between periods of testing it is maintained on nutrient agar stabs, transferred at monthly intervals.
For at least 5 days before the test the culture is transferred at 24-hour intervals to successive tubes of the meat extract broth described below and incubated at 37° C. Transfers are made with one standard loopful. The culture is filtered through sterile filter paper just before using. The test is performed with a 24-hour culture.
The phenol must comply with the requirements of the Eighth United States Pharmacopoeia. Particularly the congealing point must not be below 40° C. The crystals are kept in tightly stoppered amber-colored bottles in a dark and relatively cool place.
A 5 per cent original solution is made by adding 1 part by weight of phenol, liquefied by warming the bottle, to 19 parts of distilled water. A fresh solution is made for each day's use.
THE CULTURE MEDIUM.
3 gm. 10 gm. 5 gm.
Make meat extract medium as follows:
Beef extract (Liebig's)
1,000 c. c.
GLASSWARE AND APPARATUS,
Glassware for measuring must be accurately graduated. It must be clean, dry, and sterile at the time of use. There will be needed
1 c. c. capacity pipettes. 5 c. c. capacity pipettes. 1 c. c. delivery pipettes, graduated in tenths. 5 c. c. delivery pipettes. 100 c. c. measuring cylinders, graduated in 1 c. C., glass stoppered. Seeding tubes, 1 x 3 inches, flared tops, round bottoms.
Racks consisting of blocks of wood with rows of holes for both the seeding tubes (before they are placed in the water bath) and the subculture tubes.
Wire loops must be carefully made and kept from damage. They are made as follows: A close cylindrical spiral is made by winding a piece of platinum wire, No. 23, B. & S. gauge, as tightly as possible about a piece of steel or other hard wire having a diameter of 0.072 inch (No. 13, B. & S. gauge) to complete a little more than four full turns. The long end of the wire is then bent sharply at right angles to the wound portion and parallel to the steel wire. The core is removed and the short end of the wire is clipped off so as to leave exactly four full turns to the coil. The successive turns of the spiral must touch one another continuously. The long end of the wire is attached to an aluminum handle.
A convenient support is provided on which to rest the loops so that a batwing Bunsen burner may be placed under each one successively.
A constant temperature bath is provided, capable of maintaining the seeding tubes at 20° C. during the time of the test. A wellinsulated bath of large volume relative to the surface exposed is sufficient without thermoregulating appliances.
Disinfectant testing machine.---The use of a disinfectant testing machine is optional. One is described in Reprint No. 462 from the Public Health Reports. A few modifications have proved useful. For example, the use of platinum instead of nichrome loops, and the practice of sterilizing the subculture tubes covered with padded inverted troughs in the racks.
Dilutions of phenol and of disinfectants are made from the original liquid on the day of the test. For the dilutions of the disinfectant, a 5 per cent solution is made by adding 5 c. c. of the disinfectant to 95 c. c. of sterile distilled water. A standardized 5 c. c. capacity pipette is used for this purpose. After filling the pipette, all excess of the disinfectant on the outside of the pipette is wiped off with
The contents of the pipette are then delivered into a cylinder containing 95 c. c. of sterile distilled water and the pipette is washed out as clean as possible by aspiration and blowing out the contents into the cylinder. The contents of the cylinder are then thoroughly shaken and the dilutions up to 1:500 are made from it, using delivery pipettes for measuring. For those disinfectants which do not readily form a 5 per cent solution, make a 1 per cent solution, and from this make the dilutions greater than 1:100 in accordance with the second table of dilutions. If greater dilutions than 1:500 are to be made, a 1 per cent solution is made from the 5 per cent solution and the higher dilutions are made from this.
For the higher dilutions, delivery pipettes may be used. The following scale is used for making dilutions: For dilutions up to 1:70, increase or decrease by a difference of 5
(i.e., 5 parts of water); from 1:70 to 1:160, by a difference of 10; from 1:160 to 1:200, by a difference of 20; from 1:200 to 1:400, by a difference of 25; from 1:400 to 1:900, by a difference of 50; from 1:900 to 1:1800, by a difference of 100; from 1:1800 to 1:3200, by a difference of 200; and so on if higher dilutions are
necessary. It is important that the cylinders used for making the dilutions be correctly graduated. It is preferable to use standardized cylinders and pipettes. For making the dilutions in accordance with the above scheme, the following tables are of service:
+ + + +
1:20 1:25 1:30 1:35 1:10 1:45 1:50 1:53 1:60 1:65 1:70
0 or 10 + 0 or 4 20 + 5 or 10 + 2 or 4 20 +
10 or 10 + 5 or 4 20 + 15 or 10 + 74 or 4 20 +
20 or 10 + 10 or 4
25 or 10 + 12 or 4
10 + 13 or 4
20 + 129 or 10 + 60
or 4 + 24
or 4 20 + 50 or 10 + 2 or 4 20 + 60 or 10 + 30 or 4 20 + 70 or 10 + 35 or 4 20+ $0 or 10 + 40 or 4 20 90 or 10 + 15 or 4 20 + 100 or 10 - 30 or 1 20 + 110 or 10 7. 53 or 4
+ + +
1:70 1:50 1:90 1:100) 1:110 1:1:20 1:130
+ + +