THE TABLES: EXPLANATORY 15 



culty in obtaining successive measurements that are 

 identical on repeated examination, slight variations of 

 level in the application of the tape measure to the chest 

 giving rise to considerable variations in the measure- 

 ments, owing to the 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 knowl- 

 edge 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 cate- 

 gories as either 



(i) Normal, or 

 (ii) Possibly abnormal, 

 (iii) Probably abnormal, 

 (iv) Certainly abnormal. 



