258 DR. A. RANSOME ON GRAPHICAL REPRESENTATION 



can only be accounted for by an alteration in the chord- 

 length of the rib, due to the action of some constrictor- 

 power possessed by certain of the respiratory muscles. 



The tracings of the spasmodic and partly involuntary 

 actions of coughing and sneezing are also interesting, not 

 only from their bearing upon the mechanism by which 

 these acts are accomplished, but also because they afford 

 a strong corroboration of the conclusions drawn from 

 ordinary breathing. 



In fig. 6 it may be observed that, after the first rapid 



inspiration, which traces an oblique but almost rectilinear 

 line on the paper, there is a momentary depression, as if 

 the rib were commencing to assist in expiration ; but this 

 is suddenly stopped by the closure of the glottis, and there 

 is a slight outward bulging of the rib to the extent of 

 0*05 in. This appearance may probably be explained by 

 the continued action of the diaphragm, which compresses 

 the air in the chest, and so, to some extent, forces the ribs 

 outwards for the moment. Immediately that the air is 

 released from the windpipe, however, there is at once a 

 downward fall of the rib for a space of about 0*2 in., with 

 a barely perceptible incline inwards ; there is then a sud- 

 den change in the direction of its course, and it is drawn 

 inwards for about 0*4 in. almost horizontally, the fall in 

 this space amounting only to about 0*15 in. 



In the first part of the expiratory effort only is there 

 any similarity to the hypothetical curve given in fig. 5. 



