522 THE POPULAR SCIENCE MONTHLY. 



EXERCISE FOR CHEST DEVELOPMENT.* 



Br FEKNAND LAGKANGE, M. D. 



HOW is it that the lungs can increase in size through athletic 

 exercise ? By a mechanism well known in physiology, by 

 the filling out of certain air-cells ordinarily inactive, which only 

 come into play during forced inspiration. The expansion of the 

 pulmonary vesicles is complete in proportion to the quantity of 

 air introduced. The atmospheric air drawn into the lungs by a 

 very powerful inspiration seeks out the most obscure corners, and 

 inflates the air-cells of certain regions which ordinarily have no 

 part in the respiratory function. 



A definite increase in the volume of the lungs is the conse- 

 quence of frequent repetition of this supplemental respiration. 

 The air-cells which are as a rule inactive, and which are reserved 

 for cases of excessive respiratory strain, arise from their inaction ; 

 their walls, which are usually collapsed, and even stuck together, 

 separate and give entrance to the air which can not find room in 

 the confined space sufficient for ordinary breathing. 



If the forced inspirations are often repeated, the air-cells, the 

 action of which has thus been accidentally solicited, come in the 

 end to associate regularly in the ordinary respiratory movements. 

 They are then very quickly modified in the sense most favorable 

 for efficient working, according to the law we have so often pointed 

 out, of the adaptation of organs to the functions they perform. 



Thus, forced respirations result in a modification of the struct- 

 ure of certain regions of the lung, and in making them work 

 better. Under the influence of unusual exercise the vesicles in- 

 crease in size and contain more air. More blood is also supplied 

 to them. Their capillary network becomes richer, and their nu- 

 trition more active. Thus in the end they take up more room. 



It is in this manner that the regular working of a great num- 

 ber of air-cells, ordinarily inactive, can rapidly increase the size 

 of the lungs. 



If we follow out the modifications produced by forced respira- 

 tions, we see that the lungs thrust outward the thoracic walls to 

 make more room for themselves. During inspiration the ribs, by 

 rising, favor the inflation of the lungs ; but in this case it is the 

 lungs which, having increased in size, thrust the ribs upward and 

 keep them raised even in the condition of repose. Hence an in- 

 crease in the circumference, and a vaulted conformation of the 

 thorax. 



* From advance sheets of the author's work on " Physiology of Bodily Exercise," in 

 the " International Scientific Series," to be issued shortly by D. Appleton & Co. 



