Chap. VII. 



THE EFFECTS OF DISUSE. 



287 



110 certain conclusions could 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 sknll, 

 in comparison with these same parts in G. bankiva. 



In the following Table II. in the two first 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.' 5 



Table II. 



Names of breeds 



Gallus bankiva .. .. male 



Cochin male 



Dorking .. mala 



Spanish male 



Polish male 



Game male 



Malay female 



Sultan male 



Frizzled hen male 



Burmese Jumper . . . . female 



Hamburgh male 



Hamburgh female 



Silk fowl female 



Length 



of 

 Sternum. 



Depth of 



Crest 



of 



Sternum. 



Inches. 



Inches. 



4-20 



1-40 



5-83 



1-55 



8-95 



1-97 



610 



1-83 



5-07 



1-50 



5-55 



155 



5 10 



1-50 



4-47 



1-36 



4-25 



1-20 



3-06 



0-85 I 



5 08 



1-40 



4-55 



1-26 



4-49 



1-01 1 



1 



Depth of Crest 



relatively to the 



length of the 



Sternum, in 



comparison with 



G. bankiva. 



100 

 78 

 84 

 90 

 87 

 81 

 87 

 90 

 84 

 81 

 81 

 81 

 66 



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 the higher ranks 

 results from the attached muscles not being fully exercised. So 

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



75 The third column is calculated on the same principle as explained in the 

 previous foot-note, p. 285. 



