Page:Popular Science Monthly Volume 17.djvu/208

196 and elaborate experiments which he made on the quantities of carbonic acid thrown off by the lungs at various seasons of the year. For instance, Dr. Smith found that the quantity of carbonic acid thrown off was much greater in winter than in summer. Milner's weighings showed that the prisoners lost weight in winter, when the evolution of carbonic gas was great, and gained weight in summer, when less carbonic acid was given out.

This in itself would be a striking coincidence; but it was clearly detected that a sudden change took place between March and April, and at the same time of the year Dr. Smith found that a similar change took place in the amount of carbonic acid thrown off, and that the amount of the change was much greater at that period than at any other time; and so much greater that the alteration struck him as being a very remarkable circumstance. Dr. Smith's observations did not extend to the August-September period, and it is, therefore, impossible to say if any equally marked change takes place in autumn. There can be little doubt that variations of temperature and of light are the principal agents in causing these changes; but it will probably be found that, in addition to the direct influence of these physical agents, a periodic action in the system adds to or diminishes the effect of those physical agencies.

From the consideration of the facts collected we may fairly infer that there is a periodic variation in the weight of man during the year, the six summer months being gaining and the six winter months being losing months. The amounts gained or lost gradually increase from the commencement till the termination of each period respectively; the change from the gaining to the losing period and the converse is, however, abrupt, and these changes take place at times not very distant from the vernal and autumnal equinoxes.

Bearing on the question thus raised by Mr. Milner, I myself, from the Registrar-General's returns, made an analysis of 139,318 deaths, occurring, from 1838 to 1853, in London, Devonshire, and Cornwall, with a view of determining what causes of death were connected with the varying seasons of the year; and the result was to discover that during the wasting season, which was by far the most fatal, those diseases were most rife which spring from exposure to cold, and which are extremely fatal under that condition. I have since then many times drawn special attention to the importance of regulating clothing so as to meet the emergency to which the body is exposed during the wasting period; and the rules I had then in my mind I would enforce now. It should be a settled practice with every person in these islands that he commence to put on warmer clothing a little before the wasting period begins, and that he continue it considerably beyond the time when the balance turns and the period of increasing weight commences.

Bearing still further on this point, I have received a most practical