96 TRANSACTIONS OF THE [JaNn. 9, 
treatment of the muscles of birds in his excellent ‘‘ Key,” is stated 
by the author himself to be of the most general character; and, 
accordingly, only afew of the most important muscles concerned 
in flight are mentioned, no attempt being made to treat the an- 
atomy of the wing in detail. His single figure illustrating the 
myology of a bird shows only the outer side of the wing, while 
the new muscle occurs on the inner side, and therefore could 
not be shown in Coues’s figure. Hence the statement that the 
alleged new muscle is not given by Coues is perfectly correct. 
It was first made known, however, as my friend Dr. Stejneger 
informs me, by Vicq d’Azyr, in 1773, or one hundred and fifteen 
years ago, and has been re-described many times since in the 
works, too, of such standard authorities on anatomy as Tiede- 
mann, Heusinger, Meckel, Schépfs, Preschtl, Milne-Edwards, 
Selenka, Gervais, Alix, and many others. 
+ % *# *# Hf 
The structure of the feathers, their position and relation to 
each other, forbid any voluntary interlocking of the primaries; 
interlocking can be effected only by accident or artificial means. 
The primaries, as already stated, are so constructed that the 
inner vane of one feather supports and strengthens the outer 
edge of the next, and combines with it to form a resisting 
surface, impervious to air when the downward stroke of the 
wing is made. The barbs which form the vanes of the feathers 
are provided with recurved hooks which interlock so as to 
strengthen the vanes themselves. All the open part of the 
quills near their insertion is covered, both above and below, 
with smaller rigid and compact feathers, the more effectually to 
resist the air, Any overlapping of the quills in the inverse 
order not only rnmples and impairs the inner vane, but lets the 
air pass between the feathers, and weakens the sustaining power 
of the wing. These points are not only well known, but are 
dwelt upon in numerous special papers on the flight of birds, as 
well as in many ornithological and anatomical works, as giving 
the wing its peculiar efficiency as an instrument of flight. In 
the downward stroke of the wing no air passes through, while 
in the upward stroke the air finds easy passage between the 
vanes of the feathers. 
An important point not yet alluded to in this discussion is 
the fact that the quills cannot be interlocked when the wing is 
fully extended; it must be more or less relaxed to bring the 
outer quills near enough together to even touch at the tip, 
where the interlocking is especially claimed to occur. Itis a 
matter of observation, confirmed by the experience of every ob- 
server who has carefully noted the flight of soaring birds, such 
especially as the turkey buzzard, eagles, and hawks, that the 
