DIGESTIVE SYSTEM OF BIRDS. 



161 



brane, and by the stratum of glands which open upon its inner 





Part of the pro veutri cuius of 

 Swau dissected. 



surface, and which are its essential characteristic. 

 Hence it is by some comparative anatomists 

 regarded as a part of the oesophagus. 



The proventriculus varies, however, in 

 form and mao^nitude in different Birds. In 

 the Rasores it is larger than the oesopha- 

 gus, but much smaller than the gizzard. In 

 Eupliones ^ it forms almost the entire sto- 

 mach, the gizzard being minute : in Alcedo 

 opposite proportions prevail. In the Psit- 

 tacidcB and ArdeidcB (Parrot and Stork 

 tribe) it is larger than the gizzard, and of a 

 different form. In the Ostrich the proventriculus is four or five 

 times larger than the triturating di\dsion of the stomach, being 

 continued down below the liver, 

 and then bent up upon itself 

 towards the right side before it 

 terminates in the gizzard, which 

 is placed on the right and anterior 

 part of this dilatation. 



In the majority of Birds the 

 gastric follicles are simple, having 

 no internal cells, dilated fundus, 

 or contracted neck ; but from 

 their external blind extremity 

 proceed with an uniform diameter 

 to their internal orifice. This 

 form obtains in the zoophagous 

 and omnivorous Birds. In the 

 Dove-tribe the follicles are of a 

 conical shape ; in the Swan they 

 are tubuliform ; in the Goose and 

 Turkey they present internal 

 loculi ; in the Ostrich and Eliea 

 these loculi are so developed that 

 each gland forms a racemose 

 group of follicles, terminating by 

 a connnon aperture in the pro- 

 ventriculus. 



The subjoined figures show the different forms of the solvent 

 or proventricular glands in different Birds. 



' XXXIX-. 



Eagle. 



G an net. 



Sea-gull. 



Pigeon. 



Swan. 



Goose. 



Fowl. 



Turkey. 



Rhea. 



Ostrich. 



VOL. II. 



