428 Scientific Intelligence — Zoology. 



aerial reservoirs, annexed to the lung, are five in number on each 

 side ; Ith^ These reservoirs, being of no use for respiration, are in- 

 tended to secure the equilibrium of the bird during flight, and to di- 

 minish its specific gravity ; Qth, The air which they contain becomes 

 rarefied during inspiration, and condensed during expiration ; 9i7t, 

 The presence of air in the bones has the effect of augmenting their 

 diameter and resistance, without increasing their weight ; \^th, Fi- 

 nally, this same fluid penetrates directly into the feathers by an ellip- 

 tical orifice, situate on their under side, and serves the same pur- 

 pose in these organs as in the bony levers. 



These researches, it will be perceived, will probably have the efl'ect 

 of modifying greatly the notions generally adopted respecting the air 

 contained in the different parts of birds. 



9. On the Comparative Anatomy of the Vocal Organs of Birds. 

 By Professor Muller. — For the earliest investigations into the vocal 

 apparatus of birds we are indebted to Cuvier ; and it is to this cele- 

 brated anatomist that we likewise owe the greater part of the facts 

 relative to their organization. At a later period, M. Nitzsch 

 attempted to derive, from the study of the inferior larynx, materials 

 for the classification of birds, which has always been, as is well 

 known, one of the most embarrassing problems in the natural systems. 

 M. Muller has made a long series of observations on the v.ocal 

 organs of the passerine tribes. The results of his labours are as yet 

 but partially known ; a detailed description will soon be published in 

 the Memoirs of the Academy of Berlin. Meanwhile, we shall here 

 point out some of the general conclusions of that work, which is 

 impatiently expected, like everything else which comes from the pen 

 of the illustrious Berlin professor. 



Professor Muller concludes, from the facts he has observed, that 

 the passerine songsters cannot form a natural division ; and, contrary 

 to the opinion of M. Nitzsch, he affirms that the Ficarice cannot be 

 separated from them. The most natural groups of the order of pas- 

 serine birds contain types which diff'er in the organization of the la- 

 rynx, and the variable nature of this apparatus renders it but little 

 fitted for the purposes of classification. It is the less so, since song 

 may be produced by arrangements of structure very different from 

 each other. The passerine order ought probably to be preserved in 

 its most extended limits, comprehending even the syndactyli and the 

 climbers ; and it ought to contain, at once, birds possessing the most 

 perfect vocal apparatus, and others which seem reduced to the 

 greatest degree of simplicity. 



The two most common forms of the vocal organ among birds, are, 

 Is^, The vocal muscular apparatus, formed on the type of that of our 

 singing birds of Europe ; 2d, The form of a single muscle, thick or 

 slender. It is worthy of remark, that the first form prevails in 

 Europe and Africa, and that the second is most common in America. 

 Consequently, the forests of the Old World possess a greater number 



