8 
Jeffries on the Fingers of Birds. 
gross examination by soaking in a solution of glycerine and 
ammonia carmine. By this means I have obtained specimens 
that have shown all the bones distinctly. 
With this knowledge of the carpus and the light thrown by 
the new specimen of the Archceopteryx it would seem possible 
to decide the homologies of the fingers in the class of birds. The 
questions to be solved are: (i) Are the fingers homologous 
throughout the class? (2) Are they the I- IV or the II- V? 
'The only author known to me who considers that the fingers 
among living birds are not homologous is Dr. Coues. This dis- 
tinguished ornithologist says (Key, p. 30) : 44 The forefinger 
hand-bone sticks out a little from the side of the principal one, 
and bears on its end one finger-bone (sometimes two), which is 
commonly, but wrongly, called the bird’s 4 thumb’. For although 
on the extreme border of the hand, it is homological with 
the forefinger ; birds have no thumb (exc. Archceopteryx , 
Struthio , Rhea ) ; and no little finger.” The mistake concerning 
the Archceopteryx was natural and is merely taken from Owen’s 
memoir on the first fossil found. It has since, however, been 
shown that it had only three fingers. But why the Ostrich and 
Rhea should be included is hard to understand, since these have 
hand bones like all flying birds.* 
Among the birds with undeveloped hands the 44 index ” finger 
is the most constant, those on either side aborting before this. 
The genus Dromceus is a good example of this. 
When the hand is developed it is of precisely the same form in 
all birds. 
On the second question, which is virtually whether the first 
finger of birds is the first of the series or the second, much has 
been written ; all, however, with the idea that two were lost. 
Owen, Coues, and Morse have at separate times held that birds 
have no thumb, while Nitzsch, Meckel, Huxley, Gegenbaur and 
Rosenberg claim that birds have a thumb. 
The arguments used against the existence of the thumb are as 
follows: (1) The first fossil remains of Archceopteryx longi- 
cauda show the remains of a detached finger, which Owen sup- 
posed to be a first digit placed on the radial side of the 44 thumb.” 
Of this, however, he expresses some doubt. | (2) In Todd’s 
* See Selenka, Bronn’s Thier-Reichs, Vogel, p. 75 ; D’Alton, Die Skelete d. Strauss- 
artigen Vogel, p. 17; Owen, Anat. of the Vertebrates, Vol. II., p. 73. 
f Owen, “On the Archceopteryx .” Phil. Trans., 1864, Vol. CLIII. 
