184 



ANIMAL MECHANICS. 



Hence, the inherent work of the muscle is to the work done by 

 it as 41 to 36 ; or the work done is 88 per cent, of the inhe- 

 rent work, and the loss of work amounts to 12 per cent., in 

 consequence of the triangular arrangement of the fibres. 



In the preceding investigation, 1 have assumed that the 

 muscular fibres proceeding from AB to 0 are distinct from 

 each other, and pass continuously from origin to insertion 

 without interfering or blending with each other. On this 

 supposition, the fibres are supposed to be arranged, not in 

 one plane, but like the radiating blades of a fan, in such a 

 manner t}iat the cross section of the muscle made by a sphere 

 described with 0 as centre and with any radius, shall be 

 always constant 



In order to ascertain the law of distribution of fibres in a 

 triangular muscle, I made the following measurements in the 

 great pectoral muscle of the wing of the common Buzzard. 



The weight of the muscle was 0.705 oz. av., and the length 

 of its extreme fibres Was 6 inches. I took the breadth and 

 thickness of the cross section of the muscle at 6, 4, and 2 inches, 

 respectively, from its humeral insertion, and calculated the 

 area of the cross section from these measurements, with the 

 foiiowing results : — 



Pectoral Muscle of Buzzard. 



Distance of Section 

 from Insertion. 



Length of Section. 



Mean Thickness of 

 Section. 



Area of Cross 

 Section. 



2 inches. 

 4 » 

 6 



1.92 inches. 

 2.26 ,, 

 6.00 ,, 



0.22 inches. 

 0.07 „ 



0.422 sq. in. 

 c.418 „ 

 0.420 



1 



This Table demonstrates the accuracy of the supposition 



