12 Mr. A. Ransom e on the Mechanical Conditions [Nov. 21, 



with. Traube's observation as to the influence of the diaphragm on the lower 

 end of the bone was confirmed. The clavicles were shown to have more 

 upward than forward motion, and to move less than either sternum or ribs. 



The ribs move upward more decidedly than the sternum, their rotation 

 outwards permitting greater freedom. Their forward push is very con- 

 siderable, greater than that of the sternum, often equalling or exceeding 

 their upward rise. The upper ribs have sometimes greater forward 

 thrust than the lower ; there is no regular series in this respect in the 

 different ribs, but, on the contrary, much evidence of the independent 

 action of the several ribs. 



The greatest amount of outward motion takes place on the rib about 

 midway between the vertebral column and the sternum. 



The measurements obtained by means of the stethometer show : — 



1. That the upward dimensions of the movement are sufficiently 

 accounted for by the upward rise of the ribs, their chord-length being 

 taken as radius, their vertebral attachments as centres. 



It may be shown also mathematically that the curving of the dorsal 

 and lumbar regions of the spine in natural respiration would usually in- 

 terfere but slightly with this " upward " reading. 



2. The outward indications are also probably to be accounted for by 

 the simple radial rise of the costal ends of the costal cartilages, the 

 sternal articulation being taken as centre. 



3. The " forward " movement is, however, much more complex. It 

 could not arise from any simple alteration in the obliquity of the ribs : — * 



a. Because there is no constant relation to be discovered between the 

 amounts of " forward " and of upward movement ; and it is possible, volun- 

 tarily, at one time to produce an excess of forward, at another of upward 

 motion. 



6. Because the angles made by the ribs with the spine are not such as 

 to permit of the amount of forward movement recorded by the stetho- 

 meter. This fact is proved by measurements of these angles as found in 

 anatomical drawings, in skeletons, and in the living subject. 



In the latter the amount of forward push not accounted for by the 

 simple rise of the rib was found to be often as great as 0*5 in. for the 

 fifth rib, and 0*7 in. for the third rib. One example out of many of 

 these cases is here given. 



Case. — Male, set. 32. Strong, healthy ; 6 feet in height. 



Gross diameter over 3rd rib 8 \ in. 



Gross diameter over 5th rib 9^ in. 



Estimated chord-length of the 3rd rib 6*75 in., of 5th rib . . 7*65 in. 



Angle formed by the right 3rd rib during expiration 63° 



Angle formed by the- right 5th rib during expiration 61° 



Inspiratory angle of the right 3rd rib 78° 



Inspiratory angle of the right 5th rib 75° 



