Digestive Organs of Birds. ]29 



to the agreement of their digestive apparatus, but that the groups 

 thus produced would be perfectly natural, in respect at least to 

 their principal habits. 



It is not of much importance with what tribe of birds we begin ; 

 but as the rapacious species generally take the lead in systems, I 

 shall not deprive them of their rank. And here, once for all, I must 

 remark, that in every particular, the descriptions will be entirely 

 original, that is, the result of my own observation. 



I. Digestive Organs of the Diurnal Rapacious Birds. 



As unexceptionable representatives of the aquiline and buteonine 

 groups of this order of birds, we may take the Golden Eagle, Aquila 

 chrysa'etus, and the Common Buzzard, Buteo vidgaris. 



Plate IV. represents :-Fig. 1. the bill, 2. the palate, 3. the tongue, 

 4. the intestinal canal, 5. the rectum and cceca, of the Golden Eagle, 

 one-third of the natural size ; Fig. 6. a section of the proventriculus, 

 7- some of its glands, 8. the pylorus : — 6 and 8. of the natural size, 

 7, enlarged. 



The bill of the Golden Eagle, Plate IV. Fig. 1, is shorter than the 

 head, very deep, compressed towards the end, with a longish decurv- 

 ed tip. The upper mandible has at the base a broad cere, a, or bare 

 coloured skin ; its dorsal outline, b, is slightly convex as far as the 

 edge of the cere, then curved so as to form rather more than the 

 fourth of a circle ; the ridge, on the cere, is broad and convex, on 

 the horny part narrow but convex ; the sides at the base are nearly 

 flat and sloping, towards the end erect and slightly convex ; the 

 edges towards the base, c, are soft, being covered with skin, con- 

 tinuous with the membrane of the mouth, beyond the nostrils sharp, 

 direct, with a slight festoon ; the tip decurved, subrigonal, acute. 

 The lower jaw has the crura widely separated at the base, so that 

 the angle at the base of the horny mandible is broad and rounded ; 

 its dorsal outline, d, is convex, the back broad, towards the end nar- 

 rowed ; the sides rounded ; the edges at the base covered with skin, 

 towards the end horny, inflected and sharp, and curving downwards 

 to the tip, which, viewed vertically, is broadly rounded. The dorsal 

 outline of the upper mandible is 2i inches long ; that of the luwer 

 i§ ; the edge of the lower is 2| ; the height of the bill at the nos- 

 trils l T 2 g . 



The mouth is wide, measuring 1 T 7 ? across. The palate, Fig. 2, is 

 flat, at the sides smooth and sloping a little upwards, in the middle 

 having a longitudinal depression, a, into which the tongue fits. This 

 depression is bounded by two parallel ridges of skin, having on their 

 summit minute papillae directed backwards. In it behind the base 



NO. 11. 1 



