Penetration of ultra violet rays through animal tissues.

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Studies on the penetration of ultra violet rays for tissues were made on living animals with the quartz spectroscope and spectrograph. For this purpose rabbits, cats and dogs were used. The animals were anesthetized, the skin of the abdomen was cut open and dissected back on one side and then the barrel of the spectrograph was introduced under the skin. The skin was then radiated from the outside with Krohmayer and Hanovia Alpine Sun Mercury Vapor Lamps and a spectrophotograph of the waves which passed through the skin was thus obtained while the animal was alive and the blood circulating. In this way it was found that a considerable number of invisible ultra violet rays passed through the rabbits', cats' and dogs' skins. Thus in the case of rabbit skins varying from 1 to 2 or more millimeters in thickness, the spectrograph showed the lines in the region of 2800 angstrom units and sometimes even shorter wave lengths. In the case of the rabbit the longer ultra violet rays penetrated not only through the skin but even through the whole thickness of the abdominal wall as shown by spectrographs made with the barrel of the instrument inserted into the peritoneal cavity. Here wave lengths of 3000 angstrom units were frequently obtained with both Alpine Sun and Kromayer lamps, although the thickness of the abdominal wall (skin, fascia, muscle, and peritoneum) was usually about 3 to 4 millimeters. The permeability of dead tissue was different from living animal tissue, depending upon the state of preservation. Thus, when skin was left at room temperature and began to undergo putrefaction, the permeability was greater than in a normal living skin. On the other hand when skin was preserved either by freezing or by preservatives such as formalin or alcohol, the coagulation of proteins and other chemical changes thus produced rendered it more opaque.