632 EVOLUTION OF HEAT, LIGHT, AND ELECTRICITY. 



fluid poured out by the exhalant glands accumulates on the skin. There is 

 reason to believe that the secretion continues, even when the body is immersed 

 in water, provided its temperature be high. We learn from these facts the 

 great importance of not suddenly checking Exhalation, by exposure of the sur- 

 face to cold, when the secretion is being actively performed ; since a great dis- 

 turbance of the circulation will be likely to ensue, similar to that which has 

 been already mentioned, as occurring when other important secretions are sud- 

 denly suspended. 



3. Evolution of Light. 



666. Although the evolution of Light from the living Human subject is an 

 exceptional phenomenon, which has only been observed in morbid states of the 

 body, yet its occasional occurrence is fraught with interest to the Physiologist, 

 on the one hand from its relation to the Luminosity so common among the 

 lower animals, and on the other from the indications which it affords of the 

 possibility of the formation, even during life, of peculiar phosphuretted com- 

 pounds, which, being products of incipient decomposition, have been usually 

 supposed to be generated only after death. There is no doubt that luminous 

 exhalations frequently ascend from burial-grounds ; and that the superstitions of 

 many nations respecting " corpse-lights" have to this extent a foundation in fact. 

 A very decided luminosity has been observed to proceed from dissecting-room 

 subjects, the light thus evolved being sufficient to render the forms of the 

 bodies, as well as those of muscles and other dissected parts (which are pecu- 

 liarly bright), almost as distinct as in the day-light. That this proceeds from 

 the production of a peculiar phosphorescent compound, is shown by the fact, 

 that the luminosity may be communicated to the fingers, or to towels, &c., by 

 contact with the luminous surfaces. 1 Dr. W. Stokes narrates the case of a 

 patient who was under his observation, some years since, in the Old Meath 

 Hospital, having been admitted on account of an enormous cancer in her breast, 

 which was in an advanced stage of ulceration, the edges being irregular and 

 everted ; every part of the base and edges of this cavity was strongly phosphor- 

 escent, the light being sufficient to enable the figures on a watch-dial to be dis- 

 tinguished within a few inches;- and here also it appeared that the luminosity 

 was due to a particular exudation from the exposed surface. Three cases are 

 recorded by Sir H. Marsh, in which an evolution of light took place from the 

 living body, without any such obvious source of decomposition ; all the subjects 

 of these cases, however, were in the last stage of phthisis; and it cannot be 

 doubted that here, as in other diseases of exhaustion, incipient disintegration 

 was taking place during the later periods of life ( 418). The light in each 

 case is described as playing around the face, but not as directly proceeding from 

 the surface ; and in one of these instances, which was recorded by Dr. D. Dono- 

 van, 2 the luminous appearance was not only perceptible over the head of the 

 patient's bed, but luminous vapors passed in streams through the apartment. 

 It can scarcely be doubted that it was here the breath which contained the 

 luminous compound, more especially as in one of the cases it was observed to 

 have a very peculiar smell; and the probability that the luminosity was due to 

 the presence of phosphorus in progress of slow oxidation, is greatly increased 

 by the fact already referred to ( 570), that the injection of phosphuretted oil 

 into the bloodvessels gives rise to a similar appearance. In repeating this ex- 

 periment a Sir H. Marsh states that when half an ounce of olive oil, holding two 



1 See Sir Herbert Marsh on "The Evolution of Light from the Living Human Subject" 

 (Dublin, 1842), p. 20. From thia interesting pamphlet, most of the statements in this 

 paragraph are derived. 



8 "Dublin Medical Press," Jan. 15, 1840. 



