PAPERS OX MEDICINE AND PUBLIC HEALTH 425 



the vital capacity was as great at the conclusion of the 

 experiment as at the beginning. The investigators con- 

 clude that "general muscular weakness and fatigue of the 

 muscles of respiration are not important factors in caus- 

 ing the reduction of the vital capacity of the lungs, in 

 heart disease." 



V. Pleural Effusion. 



In a group of cases which include hydrothorax, pneu- 

 mothorax, hemothorax, and empyema, the vital capacity 

 was found to vary between 74% and 42% of the normal. 

 The vital capacity seems to depend upon the amount of 

 fluid or air in the pleural cavity, and there is a close 

 relationship between the tendency to dyspnea and the 

 decrease in the vital capacity. 



DISEASES OUTSIDE RESPIRATORY TRACT 



I. Nephritis. 



In eight cases of acute nephritis with no history of 

 dyspnea, the vital capacity was within normal limits. In 

 chronic nephritis, without evidence of heart disease, and 

 without a history of dyspnea, the vital capacity was high, 

 and within normal limits. In cardiorenal cases, dyspnea 

 was a prominent symptom, and the vital capacity usually 

 was decreased in proportion to the intensity of the 

 dyspnea. 



II. Hyper-Thyroidism. 



Dyspnea on exertion is a common symptom complained 

 of by patients with Graves' disease. This may be due to 

 nervousness, but usually indicates cardiac weakness. 

 The decrease in the vital capacity corresponds to the 

 tendency to dyspnea. 



III. Paratyphoid Fever. 



Meyers, studying the vital capacity in acute diseases 

 outside the respiratory tract, found only 15% of the cases 

 in an epidemic of paratyphoid fever, with vital capaci- 

 ties below normal. In more than half of these cases, the 

 reduced vital capacity could be explained on the basis 

 of complications, such as pleurisy or lung involvement. 



