EVOLUTION OF LIGHT. 549 



minishes, whilst that of the spring undergoes an increase; this is prohably 

 due to the greater prevalence of certain epidemics at the latter season; for 

 the same condition is observed, in a still more remarkable degree, between 

 the ages of 8 and 12 years, the time when children are most severely 

 affected by such epidemics. As the constitution acquires greater vigor, 

 and the bodily structure attains its full development, the influence of the 

 season upon mortality becomes less apparent; so that at the age of from 25 

 to 30 years, the difference between the summer and winter mortality is very 

 slight. The difference reappears, however, in a very marked degree, at a 

 later period, when the general vigor, and the calorifying power, undergo a 

 gradual diminution. Between the ages of 50 and 65, it is nearly as great 

 as in early infancy; and it gradually becomes more striking, until, at the 

 age of 90 and upwards, the deaths in January are 158, for every 74 in July 

 (a proportion of "2-> to 1) ; and the average of the three winter months is 145, 

 whilst that of the three summer mouths is only 68, or less than one-half. 

 The results of the comparisons which have now been carried out for many 

 successive years in the Reports of the Registrar-General, between the varia- 

 tions in the weekly rate of mortality in the Metropolis and the range of 

 atmospheric temperature, present a close coincidence with the foregoing: it 

 being especially to be noted, that the rate of mortality (save during the 

 prevalence of any fatal epidemic) is almost, invariably the highest during the 

 winter months ; that the increase of deaths at that period is most marked 

 amongst children and old people; and that any extraordinary severity of 

 winter cold constantly produces a great augmentation in the mortality, the 

 weekly number of deaths rising from the average of 1100 (or thereabouts) 

 to 1600 or even 1800, when the mean temperature of the week remains six 

 or eight degrees below the freezing-point. 



3. Evolution of Lie/lit. 



441. 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 com- 

 mon 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 compounds, which, being products of incipient decomposition, 

 have been usually supposed to be generated only alter 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 ob- 

 served 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 peculiarly bright), almost as distinct as in the 

 daylight. That this proceeds from the production of a peculiar phospho- 

 rescent compound, is shown by the fact, that the luminosity may be com- 

 municated to the fingers or to towels, etc., by contact with the luminous 

 surfaces. 1 Dr. W. Stokes narrates the case of a patient who was under his 



proportion of deaths during the first year of childhood occurring in the months of 

 June, July, and August, being about /bwr times greater than that occurring during 

 the same months in any subsequent year up to the age of 20. The winter mortality 

 under the second year scarcely exceeds the average of subsequent years. (Amer. 

 Jour, of Mod. Set., Nov. 1831.) 



1 See Sir Herbert Marsh, on the Evolution of Light from the Living Human 

 Subject (Dublin, 1842), p. 20. From this interesting pamphlet most of the state- 

 ments in this paragraph are derived. 



