RESPIRATION IN MAN 201 



Hultkranz estimated the average inspiratory descent of the whole 

 diaphragm at 10'5, Guillemot at 15 to 18 mm. About half an inch 

 is its ordinary descent, the right dome moving rather more than 

 the left, and the left more than the central part. From Hutchin- 

 son's, Daily's, and my own observations the area of the diaphragm 

 in contact with the lungs may be estimated at 250 sq. cm. A 

 descent of 10 mm. all over gives an increase of 250 c.c. of thoracic 

 space ; if one estimates an average quiet breath at 400 c.c. it will 

 be seen that the diaphragmatic movement plays a larger part 

 than the costal movement. Hultkranz estimated that in taking 

 a breath of 490 c.c. 170 was the result of the diaphragmatic, and 

 320 of the thoracic movement. Sewall and Pollard found that a 

 larger breath could be taken by a thoracic inspiratory movement 

 than by an abdominal one. R. T. Mackenzie has again verified 

 Hutchinson's observation that there is no relationship between 

 the extent to which the chest can be expanded in circumference 

 and the amount of breath that is thereby taken in. The thorax 

 can be enlarged so that the abdominal viscera instead of air is 

 drawn into the thoracic cavity. At the London Hospital there 

 was an old acrobat who could draw in this way all his abdominal 

 viscera up into the thorax, so that the abdominal aorta was felt 

 pulsating under the fingers from the epigastrium downwards. 

 When the thorax is expanded beyond the extensibility of the lungs 

 the abdominal viscera are drawn upwards to occupy the thoracic 

 space ; highly trained gymnasts at the army schools invariably 

 obtain their great chest expansions in this way. 



THE RESPIRATORY MOVEMENTS OF THE RIBS 



In describing the respiratory movements of the thorax most 

 teachers restrict their description to a typical rib, in order to 

 secure simplicity of description. Two movements are recognised, 

 one round an axis corresponding to the spinal articulation of the 

 rib, and another round the spino-sternal articulation. The first 

 movement gives increase of the back-to-front diameter, the other 

 of the side-to-side. Now, although in a general sense this de- 

 scription is essentially true, yet when one comes to study the 

 costal movements in the living and the arrangement of parts in 

 the dead, it is found to afford a very imperfect explanation of 

 what is seen. The ribs vary in size, shape, inclination, articula- 



