Abstract
In a previous communication 1 we have shown that thyroidectomy brings about in the course of nineteen to twenty-two days an increase in the value of the surface tension of the blood of guinea pigs. Since hypothyroidism causes this increase in the surface tension, it was of course of interest to ascertain whether the presence of excessive quantities of thyroid secretion or hormone would have the reverse effect upon the surface tension of the blood.
We therefore fed thyroxin to normal guinea pigs. The feeding was continued over a period of three to four days, and from 1 to 1.2 milligrams were fed to each animal. The animals were bled before feeding, and again on the fourth or fifth day after beginning the feedings. Determinations of the surface tension of the blood plasma were made on both of these samples. At the same times normal animals were bled and, in order to have controls of unfed animals, they were kept under the same conditions as the ones used in the experiments.
Twenty-seven animals were fed thyroxin; of these, twenty showed a rail in the value of the surface tension of the blood which was greater than 1 dyne. The remaining seven animals should a change of less than 1 dyne, some even showing a slight increase of the surface tension. The fall in the surface tension in the twenty animals varied from 1.9 dynes to 13.9 dynes. The average fall of surface tension between the first and second samples in all twenty-seven animals was 3.7 dynes; if we consider only those which showed a fall greater than 1 dyne, the average for these twenty is 5 dynes.
Of the seven control animals kept under the same conditions as the fed animals, six showed variations between the first and second determinations of less than 1 dyne, showing either a rise or a fall; one animal, however, showed a fall of 1 dyne.
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