cuAP. vn. 



THE EFFECTS OF DISUSE. 



2S7 



DO certain conclusions conld be reached. For instance, the legs of 

 the above Dorking cock were nearly three-quarters of an inch too 

 short relatively to the length of the sternum, and more than three- 

 quarters of an inch too long relatively to the length of the skull, 

 in comparison with these same parts in G. bankiva. 



In the following Table II. in the two th-st columns we see in 

 inches and decimals the length of the sternum, and the extreme 

 depth of its crest to which the pectoral muscles are attached. In 

 the third column we have the calculated depth of the crest, relatively 

 to the length of the sternum, in comparison with these same parts 

 in G. bankiva.'^ 



Table II. 



By looking to the third column we see that in every case the 

 depth of the crest relatively to the length of the sternum, in com- 

 parison with G. bankiva, is diminished, generally between 10 and 

 20 per cent. But the degree of reduction varies much, partly in 

 consequence of the frequently deformed state of the sternum. In 

 the Silk fowl, which cannot fly, the crest is 34 per cent, less deep 

 than what it ought to have been. This reduction of the crest in all 

 the breeds probably accounts for the great variability, before 

 referred to, in the curvature of the furculum, and in the shape of its 

 sternal extremity. Medical men believe that the abnormal form of 

 the spine so commonly observed in women of *^he higher ranks 

 results from the attached muscles not being fully exercised. So 

 it is with our domestic fowls, for they use their pectoral muscles 



'^ The third column is calculated on the same principle as explained iu the 

 previous foot-note, p. 285. 



