THE TABLES: EXPLANATORY 19 



mcnt what the patient's normal weight should be, then 

 look up the vital capacity corresponding to these measure- 

 ments. In this way information will be gained that will 

 subsequently be of service in determining the significance 

 of future changes in weight, vital capacity, and percentage 

 deviation from the normal. Where an individual has 

 lost considerably in weight it must be borne in mind that 

 the chest-measurement will also have become slightly less. 

 Hence the figures derived from this measurement will often 

 show a smaller deficiency than those obtained from the 

 trunk-length, which naturally shows no such change. 

 Again, however, the advantage from averaging both sets 

 of figures balances the relatively small errors introduced 

 by the change in one of the measurements. The know- 

 ledge to which class an individual is likely to belong is also 

 of particular importance when changes in vital capacity 

 are studied in connection with various diseases. 



It is perhaps worth recording that changes in the vital 

 capacity appear to offer an unusually trustworthy index 

 of any improvement or deterioration taking place in the 

 pulmonary lesions of patients with tuberculosis of the 

 lungs. It also appears from the study of a tolerably large 

 number of such cases that determinations of the vital 

 capacity and its changes may be of value in prognosis, 

 and help the physician to decide, for example, which 

 patients are likely to benefit by further sanatorium treat- 

 ment and which are not. (See "The Vital Capacity 

 Constants Applied to Pulmonary Tuberculosis," by 

 Georges Dreyer and L. S. T. Burrell, Lancet, June 5th, 

 1920, cxcviii. 1212.) 



