330 PHILOSOPHICAL TRANSACTIONS. [anNO I766. 



{)erson who made many observations in natural history, of whom he will speak in 

 his turn. These birds are: the wild swan, colum, seras, crane, Indian cock, 

 demoiselle. The structure of the wind pipe of all these is so singular and so 

 little known, that he thought a proper notice of the subject would be agreeable 

 to the R. s. 



The wild swan is somewhat smaller than the tame one; this inhabits fresh 

 rivers in land, while the wild one always resorts to great lakes and arms of the 

 sea. These are two distinct species, the river swan, and the sea or wild swan; 

 and yet it has been suggested, that the latter might become as tame and familiar 

 as the others, if they were brought up young: and hence they were supposed to 

 be the same. But this wonderful structure of the aspera arteria shows that they 

 are different, for the river swan has it not; though a very modern author, who 

 is certainly as well versed in natural history as any one whatever, has these re- 

 markable words: "All the writers on birds, says he,* have described the swan: 

 they have called it cygnus domesticus, and cygnus ferus, distinguishing it in its 

 wild and familiar state into two species, but this is idle and unnecessary, the bird 

 is wholly the same in both." It will be seen, however, by the description of the 

 part mentioned, that they cannot be the same species; for, besides this forma- 

 tion of the pipe, Mr. Edwards shows their heads to be very different also. 



In the general run of birds, the aspera arteria is nearly straight ; that is, having 

 no plications, but descending directly from the epiglottis into the cavity of the 

 body, to lie on the sternum, and terminating in the lungs; whereas, in these 

 birds, which are the subjects of this discourse, they have certain turnings within 

 the sternum or breast-bone, and run back again to double up into the thorax; 

 which elongates them to double the length of those in other birds of equal, nay 

 of greater magnitude, than the birds that have them. 



In the wild swan, the wind pipe runs down from its upper extremity under the 

 epiglottis, in company with the oesophagus, till it comes within about 4 or 5 

 inches of the last vertebra of the neck; here the pipe quits the oesophagus, 

 which keeps its course to the intestines, and makes a convex curve forward be- 

 tween the ossa jugalia, in a circular sweep, till it enters into a hole formed 

 through a strong membrane in the centre between the insertions of the ossa ju- 

 galia into the sternum under the breast ; and in that circular sweep is covered 

 closely by the skin, so that, in that place, a very slight blow would destroy the 

 bird. This hole is the beginning of a theca or cavity in the keel of the sternum, 

 in which the pipe passes on to the end, and then returns back, forming a loop 

 which is circular; and, passing out by another hole through the same strong 

 membrane, makes another circular sweep within, and parallel to the exterior one, 



• The author here alluded to is Sir John Hill. 



