74 THE MYOLOGY OF THE EAVEN. 



the whole length of the sternum. It is remarkable for 

 the length and strength of its tendon, which is inserted 

 so as to draw forwards the humerus with great force. 

 It is proportionately the smallest in the JRaptores ; and 

 is very small and slender in the Struthious birds. 



"We have already alluded to the use which the 

 Penguin makes of its diminutive anterior extremities as 

 water-wings, or fins ; to raise these after making the 

 down-stroke obviously requires a greater effort in water 

 than a bird of flight makes in raising its wings in air ; 

 hence the necessity for a stronger development of the 

 second pectoral muscle in this and other diving birds, 

 in all of which the wings are the chief organs of 



o o 



locomotion, in that action, and consequently require as 

 powerful a development of the pectoral muscles as the 

 generality of birds of flight " (loc. cit., p. 97). 



Mr. W. A. Forbes says that the pectoralis secundus 

 " in the Albatrosses is unusually short, and broken up 

 into four quite separate parts, which unite before passing 

 the shoulder-pulley. In the other Petrels, the muscle 

 is much more homogeneous, and only separable by 

 dissection into its various component parts ' (Coll. 

 Memoirs, p. 389). 



51. The pectoralis tertius 1 is the smallest of the 



1 Gadow (loc. cit., p. 252) prefaces his description of this muscle 

 by the following synonymy, he having proposed the name of the m. 

 coraco-brackialis posterior for the pectoralis tertius : 



(i 76. M. CORACO-BRACHIALIS POSTERIOR. 



Le petit pectoral. Vicq d'Azyr, 1772, p. 625 ; Cuvier. 

 Kleiner Brustmuskel. Merrem, p. 152, No. 3. 

 Pectoralis minimus. Wiedemann, p. 83. 



,, Tiedemann, 251. 



,, ,, Heusinger, p. 183. 



Prechtl, 37. 

 Coracobrachialis inferior. Meckel, System, p. 319, No. 12. 



