64 INTRODUCTION. 



grine Falcon and the Snowy Owl agree and differ are the fol- 

 lowing. In both the oesophagus is wide, the proventriciilar 

 glands very numerous and small, the stomach roundish or 

 elliptical, with thin walls, and having a rugous inner mem- 

 brane, the rectum short, with an oval enlargement. They also 

 agree in the general structure of these parts, and in various cir- 

 cumstances which it is not necessary here to point out. They 

 differ 2)rincipally in the form of the oesophagus and coeca ; for 

 while the former is uniformly wide in the Owl it has a great 

 enlargement or crop in the Falcon ; and while the coeca are 

 rudimentary and merely secrete a mucous fluid in the Falcon, 

 they are large and perform the assimilatory function in the 

 Owl. These birds may be taken as types of their respective 

 flmiilies, for all the other species which I have examined, about 

 twenty in number, agree in the principal details. One may 

 therefore in general easily recognise the digestive organs of a 

 Falconine or a Strigine bird ; and we shall see in the sequel 

 that the different families are similarly distinguishable. 



The thin stomach of these birds is of that kind usually termed 

 membranous, although they are by no means of a membranous 

 structure, but are so named in contradistinction to those which 

 have very muscular parietes, and Avhicli are commonly denomi- 

 nated gizzards. These and other modifications of the digestive 

 organs will be described in course. In the meantime we pro- 

 ceed to present a brief account of such of the other organs as 

 it may be useful to notice, taking first those immediately con- 

 nected with the digestive canal. 



Of these the first are the salivary glands, which are generally 

 simple follicles, similar to those already described in the pro- 

 ventriculus, and are situated under the tongue, along its sides, 

 and in the space behind it. In the Gallinaceous birds, they 

 form an aggregated mass in the angle of the lower jaw, open- 

 ing by several pores ; and in a few species they assume the 

 conglomerated form, and open into the mouth by a single duct. 



The pancreas, Plate lY, Fig, 4, 5, s, 5, is usually a long 

 narrow gland, always situated in the duodenal fold of the in- 

 testine, into which its secretion is poured by two or more ducts. 



The liver, Plate IV, Fig 4, ?, j, and Plate V, Fig. I, 



