INTRODUCTION 67 
asserted the truth, when he said that the general structure, but especially 
the muscular appendages, of the lower larynx was “similarly formed in 
all other birds of this family” described in Audubon’s work. Mac- 
gillivray did not, however, assign to this essential difference any systematic 
value. Indeed he was so much prepossessed in favour of a classification 
based on the structure of the digestive organs that he could not bring 
himself to consider vocal muscles to be of much taxonomic use, and it 
was reserved to Johannes Miiller to point out that the contrary was the 
fact. This the great German comparative anatomist did in two com- 
munications to the Academy of Sciences of Berlin, one on the 26th June 
1845 and the other on the 14th May 1846, which, having been first 
briefly published in the Academy’s Monatshericht, were afterwards printed 
in full, and illustrated by numerous figures, in its Abhandlungen, though 
in this latter and complete form they did not appear in public until 
1847.1 This very remarkable treatise forms the groundwork of almost 
all later or recent researches in the comparative anatomy and consequent 
arrangement of the Passeres, and, though it is certainly not free from 
imperfections, many of them, it must be said, arose from want of material, 
notwithstanding that its author had command of a much more abundant 
supply than was at the disposal of Nitzsch. Carrying on the work from 
the anatomical point at which he had left it, correcting his errors, and 
utilizing to the fullest extent the observations of Keyserling and Blasius, 
to which reference has already been made, Miiller, though hampered by 
mistaken notions of which he seems to have been unable to rid himself, 
propounded a scheme for the classification of this group, the general truth 
of which has been admitted by all his successors, based, as the title of his 
treatise expressed, on the hitherto unknown different types of the vocal 
organs in the Passerines. He freely recognized the prior discoveries of, 
as he thought, Audubon, though really, as has since been ascertained, of 
Macgillivray ; but Miller was able to perceive their systematic value, 
which Macgillivray did not, and taught others to know it. At the same 
time Miiller shewed himself, his power of discrimination notwithstanding, 
to fall behind Nitzsch in one very crucial point, for he refused to the 
latter’s PicaArI@ the rank that had been claimed for them, and imagined 
that the groups associated under that name formed but a third “ Tribe” 
—Picarti—of a great Order Insessores, the others being (1) the Oseines 
or Polymyodi—the Singing Birds by emphasis, whose inferior larynx was 
endowed with the full number of five pairs of song-muscles, and (2) the 
Tracheophones, composed of some South-American Families. Looking on 
Miiller’s labours as we now can, we see that such errors as he committed 
are chiefly due to his want of special knowledge of Ornithology, com- 
bined with the absence in several instances of sufficient materials for 
investigation. Nothing whatever is to be said against the composition of 
Ptilogonys, now known to have no relation to the Tyrannidx, were included, though 
these forms, it would seem, had never been dissected by him. On the other ‘hand he 
declared that the American Redstart, Muscicapa, or, as it now stands, Setophaga 
ruticilla, when young, has its vocal organs like the rest—a statement corrected by 
Miller in a Nachtrag (p. 405) to his paper next to be mentioned. 
1 Also printed separately as Ueber die bisher unbekannten ty ypischen Verschieden- 
heiten der Stimmorgane der Passcrinen, 4to, Berlin: 1847. 
