196 THE POPULAR SCIENCE MONTHLY. 



able 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, im- 

 possible 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 respective- 

 ly ; 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 dis- 

 eases 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 wast- 

 ing 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 com- 

 mences. 



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



