GA.STRIC GLANDS. 



181 



Fig. 183. 



common plover (Vanellus cristatus, fig. 1 85), the esophagus (a) 

 opens into the proventriculus (6), the walls of which are stud- 

 ded with gastric glands, and the 

 muscular stomach, or gizzard (c), 

 is continued into the duodenum (d) . 

 The gastric glands have their blind 

 extremities turned towards the pe- 

 riphery, and their orifices open in- 

 to the proventriculus, the granular 

 contents are there voided under the 

 most gentle pressure. These glands 

 are, for the most part, simple ex- 

 ternally ; sometimes they form 

 caecal follicles (fig. 186, B) ; they 

 are well-developed in the rasores, 

 where they are racemiform and 

 lobular (<?), or divided into many 

 clusters, as in/". The common fowl, 

 or goose, form excellent subjects 

 for study, and they can always be 

 procured in a fresh state. Fig. 187 

 represents the gastric glands in the 

 glandular layer of the proventricu- 

 lus of the common fowl ; A is the 

 gland of its natural size, and B is a 

 magnified representation of the 

 same, where the caeca appear like 

 clusters of berries attached to a 

 stem. In young birds the cellular 

 structure of these glands is very 

 conspicuous. Fig. 188, at A, are 

 seen the simple gastric glands of a 

 young owl, of the natural size ; and 

 at B, the same magnified, to shew 

 the cellular structure of these organs. The relation in which 

 these glands stand to the secretion of the gastric juice is not yet 

 satisfactorily ascertained ; the microscope shows that the orifices, 

 and inner lining of the glands, are covered with a fine tessellated 

 epithelium, whilst the parenchyma of the gland consists of 

 minute granular corpuscules, about 1 -200th of a line in dia- 

 meter, not always nucleated, but formed of an uniform granular 



