169 



transportation were paid. This matter was referred to the 

 committee just named. 



Prof. Jeffries Wyman exhibited a preparation of the wing of 

 the " Winter," or Pin-tailed Duck, (Anas acuta,) showing a 

 pecuUar arrangement of the bones and ligaments, by which, 

 when the wing is fully extended, all the segments of this ex- 

 tremity are fixed, and retained in position, independently of mus- 

 cular action ; also, when the forearm is flexed on the humerus, 

 the hand is by the same act flexed on the forearm ; or the con- 

 trary when the forearm is extended. 



The structure of the articulations of the elbow and wrist is 

 such, that during flexion and extension, the radius advances and 

 recedes upon the ulna, carrying with it the upper carpal bone, 

 and this last the hand ; in this way flexion and extension of the 

 bones is effected. The lower carpal bone is attached to the upper 

 by strong ligaments ; consequently, when the upper carpal bone 

 is drawn over the extremity of the ulna as the radius recedes, 

 the lower one is drawn up between the hand and the extremity 

 of the ulna, and acting as a wedge, maintains the hand extended, 

 until it is displaced by the reversed action of the radius. 



Prof. Wyman found the normal number of the phalanges of 

 the thumb (viz., two) in this species of duck, and also in a Bald 

 Eagle which he had recently dissected ; in each, however, the 

 thumb was terminated by a nail, which, in the eagle, assumed 

 the form of a needle-shaped spine. 



Dr. A. A. Hayes presented the following communication 

 upon Cochituate Water, in reply to the communication of 

 Dr. C. T. Jackson, presented at the last meeting : — 



I take this opportunity of presenting to the Society two copies 

 of a paper, by Dr. Bacon and myself, which was read at a meet- 

 ing of the American Academy, January 11th, 1855; and of 

 which an abstract was given to this Society, January 17th. This 

 paper was referred to by Dr. Charles T. Jackson, in a commu- 

 nication made at the last meeting. 



As both Dr. Bacon and myself have confined ourselves within 

 the limits which observation and experiment have set to research 



