no 





The zygomatie. bone* have the form of two very thin .-t v lets and are united to the square 

 bone l>y their |<o>tcrior, anil consolidated with tin- Mipeniiaxillarv by their anterior 

 extremity. The vomer separates the guttural openings of the now from one another. 



The IMMICS of the upper jaw are not fused wiih i. irh other so rapidly a- the bones of 

 the cranium. The ascending processes of the pivmaxillary and na.-al hones even remain 

 fora long time united to the frontal bone by a simple ynarthrodi;d articulation This 

 arrangement allows the upper beak to execute a certain elevating movement, of which 

 we will sjicak when describing the articulations. 



The inferior inaxilhtiy l>one is originally formed of a great nnmher of distinct 

 merits which are soon united into a solid piece. The square, petrous, or / </ tin- 

 tymfxinum ought to be considered as detached from the temporal. It is prismatic in 

 .shape, and provided on its upper surface with a diarthrodial facet which unites it t<> tin' 

 temporal, and on its lower face with another facet articulating with the branch of the 

 maxilla. Outwards it joins the zygomatic bone, and inwards with the pt'i\L'"i'l. 

 liehind, it gives attachment to the membrane of the tympanum; and in front it 

 presents a small eminence of insertion which Meckel considered a second zygomatic 

 process. 



THORAX. Sternum (fig. 73, H). The sternum of birds serving as a basis of support to 

 the muscles moving the wings, should offer, and does in fact show, a remarkable 

 of strength, because of the extraordinary volume of these muscles. And these being more 

 powerful and energetic as the bird exhibits a greater degree of aptit ude l'< >r flight, it results 

 that the structure of the sternum is solid in proportion as the bird is strong on the wing. 

 For this reason we may infallibly pronounce as to the extent and power of a bird's flight 

 by an inspection of the .sternum of individuals of its species. In this respect, howe\ 

 only announce what is well known to be a particular application of the rules established 

 by the great law of concordance between the anatomical disposition of organs and their 

 physiological finality. 



Studied in Palmipedes, which will serve as a typ;; for description, the sternum \<r< 

 itself in the form of a large rectangular cuirass, elongated from before to behind, of itself 

 constituting the inferior wall of the thoracic cavity, and also largely protecting tin- 

 abdominal cavity. Its superior face is concave, while the inferior is convex, and entirely 

 occupied by the insertion of the pectoral muscles. It presents, on the median line, a 

 thin and very silient ridge, named the lirishet (or keel), which in a remarkable manner 

 multiplies the points of attachment of these muscles. The anterior border offers in its 

 middle a small eminence of insertion, the episternal. Laterally, two articular grooves 

 are seen which correspond to the coracoids. The posterior border is cut by two not -hes 

 which are often converted into foramina. On the lateral borders are observed sm ill 

 double articular facets answering to the inferior ribs. The angles which separate these 

 two borders from the anterior are both prolonged into a little eminence, n unxl by soni" 

 authors the costal process. 



In the Fowl, the sternum is not so strong as in the Goose or Dude. On each side of 

 the brisket it shows two wide notches, which greatly reduce its substance. These 

 notches, closed in the fresh state by membranes, are distinguished as external and 

 internal. The latter, of greater size than the former, extends nearly to the extremity of 

 the bone. From this division of the lateral plates of tho sternum result two long and 

 slender processes directed backwards. The external terminates by becoming widened, 

 and forming a kind of bony plate, which covers the last inferior ribs. 



The sternum of Pigeons is distinguished by the enormous development of tho brisket. 

 The two notches of the fowl are also met with in these birds, but the internal is nearly 

 always converted into a narrow foramen. 



This comparative study of the sternum in the chief domesticated birds lea 1- n.- io 

 appreciate the correctness of the principles just enunciated, with regard to the foim ami 

 extent this bono mny exhibit. Tho Gallinaceoux Hird*, properly so called which lly 

 little and badly, have th.; sternum singularly weakened by the deep notches cut in its 

 lateral parts. With Palmipedes, the sternum is wide and" but slightly notched, HO that 

 the goose and duck, which waddle along so awkwardly in our poultry yard-, are capable 

 of sustaining long and rapid flight, like that of the wild individn ds of the same ,-| 

 With regard to Pigeons, which are well known to be swift and |x>wcrful flyers, may this 

 advantage not be due to the extraordinary development of the keel which constitutes the 

 brisket ? 



]{ibg. In the Fowl and Pigeon there an- seven pairs of ribs; and in the /><//.- nine 

 pairs. Articulated superiorly with the dorsal \. rtcbnc, as in mammals, these 1 tones are 

 provided near their middle with a Hat eminence which commences at the jxisferior 

 l>order, and in directed backwards and upwards to rest by its free extremity <>n the 

 external face of the next rib. The.se eminences (Fig. 73, '20) form an epiphysis at an 



