On the MUSCLES. 263 
But to fhew the fallacy of this, I need only to add to what 
has been before obferved, that we can perform a full infpiration, 
without bringing the upper rib, or top of the fternum, up- 
wards or nearer to our head; whereas the pretended demon- 
ftration refts entirely on the fuppofition, that all the ribs, not 
excepting the firft and fternum, have a large play upwards and 
downwards alternately. Stop the play of the firft rib, or fup- 
pofe it to be fixed in its place, which is the faa, and the boatt- 
ed demonttration is annihilated. 
Tue late opinion of SABATIER *, that both rows of inter- 
coftal mufcles ferve for expiration, and that the ribs are elevated 
by the fcaleni and ferrati poftici fuperiores, which are fixed to a 
few only of the upper ribs, fcarcely merits a comment. It is 
refuted by what is above mentioned, and by the want of the 
external intercoftals: near to the fternum, and of the internal 
near to the fpine; for intercoftals at thofe places would have 
ferved to deprefs the ribs more powerfully than in any other 
part of the thorax. 
Let us now confider the purpofe, 
First, Of the obliquity of the fibres in the intercoftal 
mufcles, and, 
SrconpLy, Of their being difpofed in two layers, the fibres 
of which decuffate each other. 
Ir is evident, that the obliquity of the fibres here is not in- 
tended to increafe their number, or the ftrength of the mufcle, 
becaufe the fibres would have been more numerous if they had 
paffed directly from the one rib to the other, or had been in- 
ferted into the ribs at right angles. 
I APPREHEND, therefore, that we are to explain the reafons 
of the ftructure in the following manner : 
NATURE, in order to give protection tothe heart and lungs, 
has formed the ribs as broad and flat as poffible, or left no 
more {pace between them than is required for lodging muicles. 
; for 
* See Anatom. T. 3. p. 465. 7. ms. 
