448 ESSAYS ann OBSERVATIONS 
nal intercoftals between the fpine and the an- 
gle of the ribs, and for the deficiency of the 
external intercoftals from where the ribs be- 
gin to turn upwards to the /rernum; a fact 
which anatomifts are now all agreed in. 
The application of the demonftration to this 
purpofe, is the intention of this paper. 
Let AB (fg. 1. Tas. viii.) be the fpine, 
CD the /ternum, EFGH, and IKLM two 
ribs; then EK and GM are lines in the di- 
rection of the external intercoftal mufcles, 
and FI, and HL are in the direction of the 
internal intercoftals. Now, fays Bayle, 
if both ribs rife, the angle FEI muft be en- 
larged, and its hypoteneufe FJ, the fibres of 
the “internal intercoftal, muft be longer: 
whereas mufcles generally are fhortened when 
they aét.—Near to the fpine, where the ribs 
cannot be brought nearer at one time than 
another, this reafoning is juft ; and there- 
fore the internal intercoftals are not placed 
nearer to the fpine than where the motion of 
the ribs is large enough to allow the lower 
rib to approach fo much to the one a- 
bove it, as to do more than compenfate for the 
elongation of the hypoteneufe of the angle 
FEI, 7. c. the internal intercofta] is only to be 
found 
