1872.] MR. A. H. GARROD ON THE GIZZARD OF BIRDS. 525 



racters. For the present, I should be inclined to leave it in a group 

 by itself, placing it in a plan of genealogical descent expressed by 

 the top of a tree (such as that so frequently used by M. Milne- 

 Edwards and Professor Flower) in a circle not far removed from the 

 great Rusa group of Asia, to which, notwithstanding the absence of 

 horns, many of the cranial characters lead me to think Hydropotes 

 most nearlv allied. 



April 16, 1872. 



Dr. E. Hamilton, V.P., in the Chair. 



A letter was read from Dr. R. Schomburgk, Director of the Botanic 

 Garden, Adelaide, South Australia, C.M.Z.S., giving particulars 

 of an instance in which a Monkey (Macacus radiatus) belonging 

 to the zoological department of that Garden appeared to have 

 exhibited reasoning powers. 



The following papers were read : — 



I. On the Mechanism of the Gizzard in Birds. 

 By A. H. Gtarrod, B.A., F.Z.S., Prosector to the Society. 



[Eeceived March 19, 1872.] 



Notwithstanding the fact that the external form and general 

 structure of the gizzard is known to almost every one, very little 

 seems to have been made out as to the means by which this organ 

 is enabled to crush and render available for nutrition the hard grains 

 taken as food. 



By most writers, the gizzard is supposed to act as a griuding-mill, 

 moving from side to side, assisted in its work by sharp-pointed stones 

 which its owner swallows for the purpose. This was evidently the 

 opinion of Hunter, though he seemed scarcely satisfied on the point 

 when he found that there was no perceptible lateral movement of 

 the muscular masses during digestion. 



Harvey gave a very good description of the action of the gizzard, 

 as far as he knew it, in his description of the abdominal viscera of 

 the common fowl ('On Generation,' Exercise vii.); and Hunter is the 

 only physiologist who seems to have worked at the subject since 

 that time. 



The structure of the gizzard as a specialized organ is best seen in 

 the Anserine birds ; and that of the Goose will be now described. 



Externally it is circular when looked at from in front, oval from 

 the side, and fusiform from above or below. The oesophagus enters 

 it as a large iufundibuliform tube, with the broader end downwards 



