RESPIRATION IN MAN 199 



the transversalis and triangularis sterni ; the rectus abdominis 

 also depresses the cartilages, but its action, owing to its peculiar 

 insertion, is really that of a depressor of the whole thorax. 

 Measurements of the respiratory movements of the subcostal 

 angle are useful in distinguishing between an inspiratory move- 

 ment effected by an upward movement of the thorax as a whole, 

 and one in which the upward movement is accompanied by a 

 tilting upwards of the outer ends of the cartilages. For instance, 

 during a forced inspiration, in three individuals, selected at random, 

 the increase at the subcostal angle was 6, 9, and 30. Unfor- 

 tunately nearly all the observations published on the movements 

 of this angle relate to forced inspiration ; in quiet inspiration the 

 increase is about 1-5 for those with an abdominal type of respira- 

 tion, and about half that amount in those with a thoracic type. 

 The writer, from observations made by the aid of X-rays, has 

 come to regard a free movement of the subcostal angle as an index 

 of a free action of the diaphragm. 



THE ACTION AND MOVEMENTS OF THE DIAPHRAGM 



In recent years anatomists have had an opportunity, thanks 

 to the discovery of Rontgen, of correcting their inferences as to 

 the action of the various parts of the diaphragm by direct obser- 

 vation on the living. When tested in this way the elaborate 

 deductions of Hasse as to the internal respiratory movements have 

 proved to be remarkably near the truth. He inferred that the 

 central or pericardial part of the diaphragm must also participate 

 in all respiratory movements, that the diaphragmatic movement 

 as a whole must be in a forward as well as in a downward direc- 

 tion, and that all diaphragmatic movements were accompanied 

 by a definite movement of the abdominal viscera. The writer 

 has shown that the diaphragm is made up of two parts which are 

 different in origin, different in their nerve supply, and different in 

 their action. These two parts are the spinal or crural part, the 

 fibres of which arise from the spinal column and arcuate ligaments, 

 and ascend to be inserted into the posterior or concave margin of 

 the central aponeurosis ; these fibres are normally from 125 to 

 150 mm. long, and weigh about 60 grammes. The other part of 

 the diaphragm the sterno-costal weighs about 96 grammes ; its 

 several digitations vary in length, that from the ninth costal car- 



