10 THE TABLES: EXPLANATORY 



tion the needle on the single-litre dial should be brought 

 back to zero by the observer. At the end of a long series of 

 examinations the spirometer should be inverted, to allow 

 any condensed moisture to escape. Five successive ob- 

 servations should be taken and recorded, the subject 

 being allowed time for a short rest after each. 



To obtain trustworthy results, it is essential that the 

 subject should be carefully shown how to proceed before 

 the actual measurements are taken. The highest reading 

 out of the five is the one that should be taken as the value of 

 the vital capacity; it is found to be about 5 per cent, 

 greater than the mean of the observations. 



THE TABLES FOR MALES AND FOR FEMALES. There 

 are separate Tables for males and for females. Such a 

 division is essential because the two sexes differ greatly 

 in almost every particular, and the results obtained by 

 using the Tables for one sex in the case of the other are 

 found to be entirely misleading. 



THE METRIC SYSTEM. It is strongly recommended 

 that all these measurements should be taken in the metric 

 system, but, as this is far from being generally adopted, 

 alternative Tables are provided in which the measure- 

 ments are given in pounds, ounces, and inches. In the 

 case of vital capacity, the measurement is always ex- 

 pressed in cubic centimetres. If, however, a spirometer 

 reading in cubic inches is used, the observer can readily 

 change the figures into cubic centimetres by means of 

 the special Reduction Table found on p. 127. 



In the case of the Tables recording pounds, ounces, 

 and inches, the accurate value in decimals of pounds 

 and of inches is set down and subsequently reduced to 

 the nearest number of ounces and eighths of an inch. 

 The reason for inserting also the decimal values in the 

 non-metric system is that use of the decimal system en- 

 ables one to determine most easily the percentage devia- 



