Abstract
In previous publications 1 , 2 it was shown that if in an allergic individual, intradermal tests be done with an offending allergen, the resulting wheal will vary in size depending upon the site of the skin injected. Larger responses occur on the trunk than on the extremities. The same discrepancy occurs in normal subjects with histamin, morphine and atropin, all of which produce wheals in normal skin. The cause of this variability in response is apparently not due to immunological factors and probably not to inherent lack of response in the capillaries. Consequently, there seems to be some other participating factor and this was sought in the skin tissue itself.
Advantage was taken of the fact that a histamin wheal in a dog's skin is similar in time of formation, shape and histological picture as that in human skin. Moreover, the same discrepancy in size of wheal formation at various sites, to an intradermal injection of a constant amount of a given strength of histamin occurs in a dog just as it does in humans.
Dogs were anesthetized with amytal and a portion of the shaved skin of the abdomen dissected off. This was washed in 0.85% sodium chloride solution until free from blood. The subcutaneous fat was dissected off and the skin cut into fine pieces. Ten grams of washed chopped skin were placed in 90 cc. of 0.85% saline solution to which sufficient histamin phosphate had been added to make a final dilution of this drug 1 to 10,000. The mixture was thoroughly shaken at intervals for 2 hours and filtered. For a control, proportionate amounts of skin and saline solutions without histamin were prepared in the same way.
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