448 



Mr. W. North. The Influence of 



of my own body-weight were often very considerable, and this is 

 especially the case between the evening weight and that of the follow- 

 ing morning : variations during the day may be very largely due to 

 food and drink, particularly the latter. This loss of weight during 

 sleep is due to two causes, loss by the skin and lungs, and loss by the 

 kidneys, as I always emptied the bladder before taking my weight. 

 Making all allowance for the urine, it is clear that whilst sleeping 

 I frequently lost 1 to 1-J lbs. in weight, and on some occasions even 

 more, by the skin and lungs alone. During the day I have frequently 

 observed even greater loss from this ca/use. 



The object of frequent and regular observations of the body- weight 

 in all investigations of this kind is to determine whether or no there 

 exists a relation between loss of tissue and discharge of nitrogen. 

 The weight of proteid which would represent the greatest increase in 

 the nitrogen discharge I have ever observed is very small compared 

 with the variation of body-weight from other causes, and is very 

 liable to be overshadowed by them, if indeed we ought to consider 

 ourselves in any degree capable of distinguishing between the two. 



There are a number of circumstances which affect the body- weight, 

 and which I think it would be well briefly to consider: They may be 

 divided roughly into two categories, external and internal. 



External Conditions.— -The condition of the atmosphere, height of 

 the barometer, external temperature, and the nature of one's occu- 

 pation. 



It is a matter of common observation that the amount of sensible 

 perspiration varies very materially with meteorological conditions, 

 and I have good reason for believing that not merely the sensible 

 perspiration is affected, but also indirectly the total loss through the 

 skin. 



Speaking for myself, and I have often heard the same remark made 

 by others accustomed to severe physical exertion, a low barometer 

 and the depressing conditions which so often accompany it pro- 

 foundly influence the effect of such exertion upon the body- weight ; I 

 can only suppose that this is due to the mental effect produced 

 reacting on the vasomotor system. Nor is this all. I think that 

 there is evidence in the results of my experiments, that this effect 

 manifests itself in another way,* which unfortunately seriously com- 

 plicates the problem I have set before me for solution. This vaso- 

 motor action affects the blood supply not merely of the skin, but also 

 of the internal organs, and especially the kidneys, causing not only a 

 great increase in the quantity of urine, but also an increase' of 

 excretory activity, which has for result an incontestable increase in 

 the amount of nitrogen in the urine. This makes it exceedingly 

 important in estimating the value of results obtained to take very 



* E. Smith : "Health and Disease," 1875, p. 157. 



