PAPERS OX MEDICINE AND PUBLIC HEALTH 429 



confirm the physical examination. A few patients under 

 estimate their respiratory discomfort on exertion. The 

 vital capacity is lower than one would expect from the 

 history. Exercise tests will demonstrate the patient's 

 reserve is much less than he has stated, and here again 

 the vital capacity determination is a helpful check on the 

 history. In other cases, in which the history of dyspnea 

 seems out of proportion to the results of physical ex- 

 amination, the vital capacity may be low. In these pa- 

 tients, the course of the disease will confirm the value of 

 the history and vital capacity, and shows that the physi- 

 cal examination gives an inadequate conception of the pa- 

 tient 's reserve. 



It is important to appreciate that changes in the vital 

 capacity of the lungs are an index of the clinical condition 

 only in-so-far as the cardiac weakness shows itself chiefly 

 by producing dyspnea. This is frequently but not in- 

 variably the case. Certain patients with cardiac disease 

 are restricted in their activities by the occurrence of 

 palpitation or by pain rather than by becoming short of 

 breath. The vital capacity of the lungs has no direct 

 connection with palpitation or pain, and in cases in which 

 these are the presenting symptoms, it does not bear any 

 relation to the condition of the patient. 



The cause of the decrease in the vital capacity of the 

 lungs in heart disease has never been adequately ex- 

 plained. In advanced cases, it is due in part to pulmon- 

 ary edema, pleural effusion, hepatic enlargement, and 

 similar other factors, but in many cases, the vital capac- 

 ity is decreased without any physical signs which can 

 account for it, or with physical signs which are insuf- 

 ficient to explain the extent of the decrease. Siebeck sug- 

 gests that this decrease in the vital capacity may be due 

 to an engorgement or overfilling of the pulmonary ves- 

 sels, and a consequent diminution of the elasticity of the 

 lungs. Drinker. Peabody and Blumgart produced pul- 

 monary congestion and a subsequent low vital capacity 

 in cats by compressing the pulmonary veins at their en- 

 trance into the left auricle. From these experiments, it 

 appears that the vital capacity may be reduced by en- 

 croachment of the dilated capillaries on the alveolar 



