A simple coagulometer / by H.H. Dale and P.P. Laidlaw.

  • Dale, Henry Hallett, 1875-1968.
Date:
1912
Catalogue details

Licence: In copyright

Credit: A simple coagulometer / by H.H. Dale and P.P. Laidlaw. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    blood and immersion of the tube in the bath. With a little practice 6 to 8 is enough. By turning the handle of the clip between the fingers, the tube is rotated to and fro so that the shot runs gently up and down. If the relations of size between shot and tube given above are adhered to, the shot runs easily and is clearly visible in a good light. For about four-fifths of the time between the shedding and coagulation of the blood, the tube can be held nearly horizontal in the bath, the running of the shot being secured by slight tilting to and fro. Then an almost sudden increase in viscosity of the blood is observed, and presently the tube has to be held almost vertical to keep the shot travelling. Unless the tube is jerked or knocked, how- ever, the shot should continue to travel smoothly up and down, but with diminishing speed, till it stops altogether with the tube held vertical. At this point, which can be distinguished with some accuracy, the watch is stopped and the reading taken. Shaking the tube will probably dislodge the shot, but this will stop again after falling along part of the tube. Doubtless other end-points could be devised with the same apparatus, but we have found this moment, when the shot stops dead with the tube held vertical, the most convenient. We have repeatedly verified the fact that, when the tube is cut open at this moment of stoppage, the shot is found entangled in delicate clot. What we measure is the time after which, in the given apparatus, the clot attains just sufficient consistency to support against gravity a spherical leaden shot of the given mass in a tube of the given diameter. Results Obtained. A. Uniformity. Before showing the effect of varying conditions, we may quote a series of observations which indicate the degree of accuracy attainable when all conditions are constant. We usually took a group of from four to six readings, in as rapid succession as convenient, and took the mean as the figure for one observation. A number of such groups are quoted in succeeding sections, and the scale of accuracy can be gathered from an inspection of these groups. The readings so ob- tained from any one individual at a given temperature showed a remarkable consistency over a period of days, when taken at different times in the day and with varying relation to meal-times. Thus in one individual twenty-four readings, in five groups, were taken at 38° C. over a period of ten days. The highest individual reading was 1' 5CU, the lowest 1' 3 2, the average of the twenty-four readings 1' 4:1'5, the mean error 4*3. The consistency appears more striking if we compare the mean values obtained by averaging each group of readings separately, the five values being 1/41//, l/42//, l/42//, l/42//,
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