Abstract
The mechanism by which capillaries permit dyes and particulate matter to escape in increased amounts is not clearly understood. Many investigators have observed certain physiological and pathological changes in experimental animals in which the capillaries were more permeable than normal. Burrows 1 and Menkin 2 have stated that trypan blue and India ink when injected intravenously localize and concentrate in areas of inflammation. The latter has also shown that such substances when injected into areas of inflammation are retained longer than when they are injected into normal tissue.
Recent studies in this laboratory have shown that trypan blue and India ink do not always concentrate in areas of inflammation produced by the local application of xylol in the skin of rabbits. These substances concentrate in such areas only when they are injected into the circulation immediately or within a period of less than 5 hours following the application of the xylol. The fact that trypan blue and carbon particles fail to concentrate in xylol-treated areas of skin is very interesting since these areas of skin after 5 hours show all the macroscopic and microscopic changes associated with inflammation.
The rabbits were carefully shaven 24 hours or longer before they were used in these experiments. Areas of skin on the sides of these animals were outlined in India ink. Xylol was carefully applied to these areas with a cotton swab. Care was taken not to massage the skin during the application of the irritant. Frequently the xylol diffused along the surface of the epithelium outside the areas marked out with the ink. The skin became blanched immediately following the application of xylol and within a period of less than a minute thereafter it became hyperemic.
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