194 Mayow 



action, as for the former, which is indeed a very difficult 

 one. 

 < And here it should be noticed that the ribs are 

 joined to the spine, not as is commonly believed with 

 a single but with a double articulation, and that these 

 joints are placed so obliquely, and shaped with such 

 contrivance, that the ribs cannot be raised by the 

 intercostal muscles without being at the same time 

 drawn outwards for the greater dilatation of the 

 chest, as is clearly seen in Plate II., Fig. 5 : in which 

 let «, e^ iy be a portion of a rib whose round head, «, 

 enters c, the socket hollowed in the spine ; this 

 articulation is superior and interior. On the con- 

 trary, in the other articulation, the lower and 

 exterior, a cavity, but a less conspicuous one, is 

 hollowed out in the rib at ^, and is articulated with 

 the protuberance of the spine at b. And now, if we 

 suppose the head, ^, of the rib to be placed in the 

 socket, c, of the spine, and the hollow of the rib, ^, to 

 rest on the protuberance, b^ of the spine, and then 

 the rib connected with the spine by these two 

 articulations to be moved upwards, it is easily under- 

 stood that the rib will be carried to the left, or, what 

 is the same thing, outwards, in respect to the chest. 



These articulations, and also their obliquity, are 

 more noticeable in the skeleton of a sheep or of a horse 

 than in that of a man. For it is to be observed that 

 these articulations are much more oblique in some 

 animals than in others ; in animals, namely, which, 

 destined for more violent exercise, have need of more 

 violent respiration, the joints of the ribs are very 

 oblique, in order that their ribs may be drawn more 

 outwards by the contraction of the intercostal muscles, 

 and that space enough may be opened in the chest 

 for a sufficiently large expansion of the lungs. 



