Tables I and II summarize the experience with the various salts in different concentration in the tubes and in 100-c. c. bottles.

TABLE I.-Influence of anticoagulants on beef blood in tubes.

TABLE II.-Influence of anticoagulates on beef blood in 100-c. c. bottles.

Bottles that did

11

6.8

4

7.7

41

2.0

18

3.3

19

4.0

1

64

19

606

9

0

0

27

28

From Table I it will be noted that the 0.2 per cent potassium oxalate and the 0.2 per cent sodium fluoride preservatives were the most satisfactory in preventing coagulation; and Table II shows that in one case with 0.2 per cent potassium oxalate, when 36 tubes were tested, none had clotted at the end of 219 days.

With any of the salts there is a gradual darkening of the blood on standing, but this change is more marked when the oxalate is used, in which case the sample frequently becomes almost black. Also, on standing, the cells may settle out from the plasma, but a good mixture may be obtained again by shaking.

INFLUENCE OF PRESERVATIVE ON CARBON MONOXIDE CONTENT.

To determine whether the preservative caused any change in the carbon monoxide content, when there was a delay between sampling and analysis, and also to determine the effect of the presence of air in the tubes, the following parallel experiments were performed:

Into 100-c. c. bottles were measured 0.2 gram of potassium oxalate, 0.3 gram of sodium fluoride, or 0.4 gram of sodium citrate in the form of dried salt. The bottles were fitted with cork stoppers covered with tinfoil and were sterilized with dry heat. Carbon monoxide was bubbled through three absorption tubes containing beef blood, the order of their positions relative to the gas coming from the generator being changed from time to time so as to promote equal saturation. The carbon monoxide content was determined by the Van Slyke method, as modified by the writers." The blood was then poured into a vial, or drawn up into a vaccuum tube by breaking

5

FIG. 2.-Changes taking place in blood samples kept in different preservatives in Keidel tubes.

the neck of the ampule below the surface of the liquid. The tubes were kept mostly in the darkness of a laboratory closet, thus preventing a possible loss in carbon monoxide hemoglobin from the influence of light. To complete the resemblance of their treatment to that experienced by a sample sent through the mail, they were shaken daily. At intervals of two days the carbon monoxide con

• Prepared by allowing formic acid to drop into concentrated sulphuric at 150°, washed through potassium hydroxide, and kept over water.

The determination of carbon monoxide in blood. By D. D. Van Slyke, and H. A. Salvesen. Biol. Chem., vol. 40, Nov., 1919, pp. 103-107.

Solubility of carbon monoxide in serum and plasma. By H. R. O'Brien and W. L. Parker. Jour. Biol. Chem., vol. 50, 1922, p. 289.

7 The action of light on carbon monoxide hemoglobin. By H. Hartridge. Jour. Physiol., vol. 44, 1912, pp. 22-33.

PER

C.C. OF BLOOD.

tent of one tube of each set was determined on the Van Slyke apparatus. Unfortunately the citrate series was cut short by clotting. The curves in Figure 2 show the change which took place on standing, due to the preservative.

The tests as shown by these curves prove that there is no appreciable change in the carbon monoxide content when samples of blood are stored in the Keidel tubes over a period of two weeks, and that the three preservatives tested (sodium citrate not for full time) gave the same amounts of carbon monoxide, at least within the experimental error of analysis.

FIG. 3.-Changes taking place in blood samples kept in different preservatives in Keidel tubes and vials.

At the same time that the above tests were made, a second series of blood samples was prepared in which vials having screw-cork stoppers and plain cork stoppers, along with Keidel tubes, were used to collect the samples. In some cases the tubes were only partly filled in order to determine the effect of air on the carbon monoxide content. The results are shown in Figure 3. The curves in this figure show the carbon monoxide content in the blood to be practically constant for each of the preservatives tested, even at the end of 14 days.

When the blood is treated with sodium citrate or fluoride, neither the salt nor the standing has any appreciable effect on the carbon monoxide content, although in some instances the presence of a large proportion of air results in a slight decrease in the carbon

monoxide content. In the case of oxalated blood there was a small drop (fig. 3) in carbon monoxide, which is accentuated by the presence of air. There was always a loss of oxygen and an increase of carbon dioxide in the blood samples; this was most rapid with oxalated blood and most delayed with blood treated with fluorides.

DEFECTS IN METHOD.

Under the most favorable conditions there will, at times, be some delay in filling the tube with blood or in getting the salt well dissolved and distributed. Some clotting does take place in spite of precautions, though this has been reduced to a minimum. The manipulation of the tube calls for some skill on the part of the person taking the sample, though ordinarily but little more than is required to secure a Wassermann specimen. A long needle may be necessary for cardiac puncture on a subject who has been killed by carbon monoxide asphyxiation.

SUMMARY.

1. A modified Keidel tube method, by which 10 to 15 c. c. of blood may be collected in the field, shipped to a central laboratory, and kept with slight chances of clotting or change in carbon monoxide content has been described. If such a tube is not available, a small vial, well stoppered with a cork, will serve satisfactorily.

2. Sodium or potassium oxalate (0.2 per cent), sodium fluoride (0.3 per cent), and sodium citrate (0.4 to 0.8 per cent) inhibit coagulation, the last-named being the least efficient. Oxalate causes some change in the blood, with a slight altering of the carbon monoxide content. The fluoride is recommended because it is not open to these objections.

3. No change in the amount of carbon monoxide in the blood has been detected from standing when 0.3 per cent sodium fluoride is used.

Acknowledgments.-The writers wish to express their appreciation to A. C. Fieldner, Superintendent of the Pittsburgh Experiment Station of the Bureau of Mines, Department of the Interior, who supervised the work; to Dr. J. C. Burt, who placed the facilities of the State clinic at our disposal in gathering specimens of human blood; and to W. H. Parker, junior chemist at the Pittsburgh Experiment Station, for performing a major part of the analytical work.

55086°-23-2

AUTOMOBILE COST IN RURAL HEALTH WORK.

Report on Operation of Automobiles in Cooperative Rural Health Work in Virginia. By H. MCG. ROBERTSON, Surgeon, United States Public Health Service, in charge of cooperative rural health work in Virginia.

A complete and accurate record regarding the cost of operating small 22 horsepower automobiles in county health work in Virginia is given in this report. It is thought that the figures might be of interest to officers of State departments of health and of other organizations engaged in rural health work, particularly as it is believed that the conditions under which these cars were operated in Virginia were such as to make possible a fairly accurate estimate of the general average cost of this type of motor transportation in county health work.

Accurate monthly financial statements are made out for each county in which cooperative rural health work is being done. All bills presented monthly to the State board of health by the sanitary officer of each county are used in making up these financial statements. These bills are paid by check and are on file in the Division of Cooperative Rural Sanitation of the Virginia State Board of Health. Mention is made of these facts in order to show the sources of the figures pertaining to the operating costs as given in the accompanying tables.

It will be noted that the three and a half years considered are divided into two periods. The first, from May 1, 1919, to June 30, 1921, comprises those months during which the cost of nearly all supplies was abnormally high. It was also the experimental period in this rural sanitary work-experimental as regards both methods and the men who operated the cars.

The second period begins with July 1, 1921, the time when prices of supplies began to decline. By this time, too, the county sanitaryofficer problem had become somewhat stabilized, as is shown by the fact that 7 of the 11 sanitary officers engaged in rural health work in Virginia at the time of this report were so employed prior to July 1, 1921. The other 4, serving principally in new counties, have proved themselves efficient car operators as well as sanitary officers. Thus there are several factors that must be considered in accounting for the decline in operating costs seen when the two periods are compared.

It will be noted that the average monthly cost of operation for the first period is $46.06, and that for the second period it is $35.94, a decline of $10.13 per month. When the full three and a half years-357 car-operating months-are taken together, the average monthly cost is $41.69. (It is probable that for any new county health project of the type in effect in Virginia this last figure, $41.69, would be the safest to consider or adopt.) This $41.69 operating expense plus the $25 per month charged as rental for a replacement