HERMANN VON HELMHOLTZ 



attachment moves forwards, and thus the ribs and 

 their cartilages are submitted to torsion. Thus each 

 rib-ring has a kind of elasticity like that of a hoop 

 lying on a plane surface, and is stretched antero-pos- 

 teriorly until it is slightly oval, and the thorax may 

 be regarded as built up of such a series of rings. Each 

 ring is in a position of stable equilibrium, until it is 

 submitted to the muscular effort of inspiration, and 

 to which it springs back by its elasticity. He also 

 demonstrated the greater mobility of the upper part 

 of the chest in the female than in the male. Finally, 

 he took the view, that the external intercostals were 

 inspiratory, while the internal had more to do with 

 abdominal breathing. 



Somewhat later in the same year, he lectured on 

 the muscles of the arm, and gave the result of obser- 

 vations made both on the cadaver and on the living 

 subject. Most of the actions described are now 

 found in all anatomical books. He described speci- 

 ally the movements of the clavicle and scapula. He 

 then gave an account of the possible movements of 

 the arm at the shoulder joint, supposing the arm to 

 be extended at an angle of 45, with the flexor 

 surface directed forwards. He accurately defined 

 three axes of rotation, one horizontal from before 

 backwards, a second parallel to the length of the 

 upper arm, and a third perpendicular to the two 

 former. As regards the process of supination of the 

 170 



