

CONNECTED WITH THE SHOULDEB-JOINT. 137 



show that the rectus abdominis may be considered to be a special- 

 isation in one animal of one, and in another of the other of these 

 muscles. Neither is evidence wanting* to show that the recti 

 abdominis should, instead of being placed in a class by themselves, 

 have the pectorales as well as the obliqui ranked with them *. 



Thirdly, a copiously illustrated memoir on the subject of this 

 paper, ' Die Muskeln der vorderen Extremitaten der Reptilien und 

 Vogel/ by Dr. Riidinger, of Munich, has come into my hands quite 

 recently. In it, however, I can find no views enunciated as to the 

 homology of that most distinctively avian specialisation the pecto- 

 ralis secundus. At p. 105, however, of this memoir I find a state- 

 ment as to the muscles of saurians which confirms the view I had 

 previously formed as to the homology of the muscular bellies 

 which pass in certain animals (see p. 133) from the scapula to the 

 forearm with the hamstring muscles of the lower limb. His words 

 run thus : — ' Nur erhebt sich zwischen dem lateralen Kopfe (des 

 Triceps) und dem Deltoideus ein vom Schulterblatt besonderer lang- 

 licher Muskel, welcher da, wo gewohnlich das Ligamentum inter- 

 musculare externum angebracht ist, nach unten gelangt, an der 

 Beugeseite des Vorderarms Verstarkung erhalt, und, theilweise mit 

 der Aponeurose der am untern Ende des Humerus entspringenden 

 Muskeln zusammenhangend, seinen Ansatz mit einer diinnen runden 

 Sehne an der Beugeseite des Radius findet.' 



Finally, I should add that I have strengthened the conclusions 

 which I laid before the Linnean Society in June last by employing, 

 as suggested to me at the meeting by Dr. Boycott, the evidence 

 which may be drawn from the facts of innervation. But as this 

 line of evidence has not, so far as I know, been touched upon in 

 any other memoir upon this subject, I have not thought it neces- 

 sary to keep the particular arguments which belong to it apart 

 from the rest of the text. 



1 See Mivart, 'Proc. Zool. Soc.' June 27, 1867, p. 776; Meckel, 'Vergleich. 

 Anatomie,' iii. pp. 155, 197 ; Ecker, 'Anatom. Frosches,' p. 95. See also the descrip- 

 tion of fig. 3, ei, on p. 138. 



