422 ILLINOIS STATE ACADEMY OF SCIENCE 



a vital capacity of about 4,000 c. c, and with each gain 

 of 0.1 square meter the vital capacity goes up 350 c. c. 

 From these data, we can conclude that a normal male 

 between the ages of 20 and 30 has a vital capacity of 2.5 

 liters per square meter of body surface, and that a nor- 

 mal female between 20 and 30 has a vital capacity of 2 

 liters per square meter of body surface." The maximum 

 respiratory exchange remains practically constant up 

 to 50 years, after which there is a gradual decline — great- 

 est between 50 and 60 years, and reaching 50 per cent 

 of the normal at 85 years. 



RESPIRATORY DISEASES 



I. Tuberculosis. 



Meyers, studying the vital capacity in tuberculosis, 



found a direct relation between the extent of pulmonary 



involvement and the degree of the lowered vital capacity. 



On the basis of roentgen-ray examination, he classed 



the cases as follows: 



I. Suspected cases in which roentgen-ray examina- 

 tion was negative. 

 II. Tuberculous cases. 



A. Peribronchial with unilateral and bilateral 

 involvement. 



B. Parenchymatous 



1. Unilateral with 



a — the disease confined above the 

 first rib or an area of similar 

 size. 



b — With the disease extending be- 

 low the first rib but not involv- 

 ing more than one lobe. 



c — involving more than one lobe. 



2. Bilateral. 



a — Disease confined above the first 

 rib, or an area of similar size 

 on each side. 



b — Disease extending below first 

 rib, on each side but not involv- 

 ing more than two lobes. 



c — Involvement of more than two 

 lobes, 



