Mr. Le Gros Clark on the Mechanism of Respiration. 133 



the respiratory movements are observed whilst the usual tight dress is 

 worn, and when the figure is at liberty to expand more naturally on 

 removal of the dress. 



28. Moreover, the form of the bust in the female lends a further aid to 

 the influence of dress, by exaggerating the thoracic movements. Thus in 

 stout women with full bosom, the rise and fall of the chest is much more 

 apparent than in those in whom the bosom is spare and ill developed. 

 This may be partly accounted for by the greater interference which is due 

 to the increased compression exerted to reduce the size of the waist by 

 stout women, but not wholly so. An artificial arrangement on the upper 

 part of the chest of the male, by which prominence is given to this region, 

 when the waist is compressed, at once exhibits distinct thoracic movements 

 which were not otherwise perceptible. I am disposed, therefore, to believe 

 that the asserted natural difference in the respiration of the two sexes is due 

 to the altered form of the chest, consequent on compression, and to the 

 habitual confinement of the lower costal region, which necessitates the habit 

 of thoracic breathing. It is to be regretted that experiments to determine 

 this question have not been conducted in some uncivilized community, which 

 has not attained to the cultivated refinement of endeavouring to improve the 

 natural symmetry of form at the expense of health and comfort. I am not 

 aware that any such attempt has yet been made. 



P.S. — Since writing the above, I have had the opportunity of conversing 

 with M. Duchenne, who performed some experiments with electro-magnetism 

 at St. Thomas's Hospital to demonstrate the action of various muscles. 



He expressed himself strongly respecting the action of the intercostals 

 as exclusively muscles of inspiration. This opinion is based partly on 

 experiments performed upon decapitated criminals, and partly on clinical 

 observations in cases of muscular atrophy. Immediately after death 

 M. Duchenne applied the stimulus of an interrupted current to the in- 

 tercostal muscles, with the result of raising the ribs. He stated that he 

 isolated as far as possible the external from the internal set of muscles, 

 and found stimulation of either set produced the same result. I give 

 these statements as I received them, but I did not witness the experiments 

 referred to. 



The following are the chief points, either disputed or not previously re- 

 cognized, which it is the object of the preceding observations and experi- 

 ments to establish : — 



1. The normal state of the diaphragm, when at rest, is that of arched 

 tension ; and this condition is due to the elasticity of the lungs resisting 

 the atmospheric pressure on its thoracic surface. 



2. This tension is such that the diaphragm cannot be forced upwards 

 whilst the ribs are fixed ; and is exerted in drawing the ribs inwards when 

 the intercostal muscles are relaxed. 



