14 THE TABLES: EXPLANATORY 



interference of the mammary tissue. The errors thus 

 introduced are, however, small when averaged up by 

 basing the calculations on both trunk-length and chest- 

 measurement, where individual cases are concerned. 



If, on the other hand, one wishes to compare the 

 weights of a whole group or class of individuals with 

 those of another group or class, little advantage, if any, 

 is gained by averaging the figures obtained from both 

 these measurements. At the present stage of our know- 

 ledge it would seem that if greater deviations are found 

 to occur by taking both measurements into account than 

 by basing the calculations on trunk-lengths only, the 

 latter series of observations should be considered the 

 more correct. 



These remarks on the weights derived from trunk- 

 lengths and chest-measurements apply equally to estimates 

 of the vital capacity based on these two measurements. 



What has been said above in the case of females applies 

 also to a certain extent to males, though in males it is 

 easier to obtain accurate chest-measurements. 



Variations in the Normal Weight. No hard-and- 

 fast line can be drawn between the normal and the ab- 

 normal when the weight of the body is being considered. 

 It is best therefore to class body- weights in four categories 

 as either 



(i) Normal, or 

 (ii) Possibly abnormal, 

 (iii) Probably abnormal, 

 (iv) Certainly abnormal. 



The Tables having been applied to a large number of 

 observations, it can be stated that if an individual is 

 found to be as much as 5 per cent, below or above normal 



