178 THE VOYAGE OF H.M.S. CHALLENGER. 



The Stomach. 



As already remarked, it is impossible, owing to the gradual transition from the 

 oesophagus to the stomach, to decide, on the strength of a merely external examination, 

 where the former ends and the latter begins. An inspection of the interior of these 

 organs, however, enables us to fix the position of the anterior border of the proventriciilar 

 glandular patch, and this border sufficiently indicates the separation between these 

 two portions of the alimentary canal. This border corresponds pretty closely on the 

 exterior of the viscus to the posterior border of the left lobe of the liver. From 

 it to the posterior extremity the stomach measures 4 inches in length. The trans- 

 verse diameter of the glandular portion of the stomach, measured externally, is 

 1^ inches, and that of the muscular portion, both in respect of longitudinal and 

 transverse measurements, is the same. The stomach extends from the posterior border of 

 the left hepatic lobe obliquely backwards and to the right, its j^osterior extremity 

 occupying the middle line of the abdominal cavity immediately in front of the globular 

 cloaca (PI. XVI. fig. 9). To the right of the stomach are the coils of the small intestine, as 

 well as the gall bladder, while on the left the stomach lies in contact with the abdominal 

 wall. The stomach is cylindrical in form, except at its posterior extrfemity, where it is 

 somewhat flattened from above downwards, and is attached to the vertebral column by a 

 double fold of peritonaeum or meso-gastrium. Externally it is divisible into two portions, 

 (PI. XIII. fig. 3), an anterior, ovoid in form, which, from the fact that it contains the pro- 

 ventricular gland may be named the glandular portion, and a posterior of much smaller 

 size, which presents on either surface a slight indication of a central tendon, from which 

 the muscular fibres composing its walls radiate as from a central j)oiut. The latter corre- 

 sponds to the gizzard of other birds, and may be termed the muscular portion of the 

 stomach. These two portions when the viscus is empty are separated externally by a 

 well-defined constriction. Immediately behind the pyloric orifice the muscular portion 

 of the stomach dilates into a small pouch-like diverticulum, which lies to the right side 

 of the viscus. 



On opening the stomach by means of a longitudinal incision carried along its left 

 margin, its two portions (PI. XIII. fig. 4) are seen to present very difi"erent characters. 

 The anterior or glandular compartment is lined by a soft succulent mucous membrane, 

 which on the right side of the stomach is raised above the surrounding level through 

 the presence of a well-defined ^^atch of subjacent proventricular glands. This ^^atch does 

 not form a continuous belt of uniform breadth, as in the majority of aquatic birds, but is 

 triangular in form, and is confined to the right wall of the stomach. The base of the 

 glandular patch corresponds on the inside of the stomach to the constriction which 

 externally separates the glandular and muscular portions of the organ, while its apex is 

 directed forwards towards the mouth. From base to apex the proventricular gland 



