255 
boné, and firmly bound together by a strong ligamentous band com- 
posed of interlaced fibres. On its upper surface rests the uropygial 
gland, celebrated by the field- and closet-naturalists, being one of the 
few points of the structure of a bird accessible to them, and contain- 
ing a quantity of oily matter mixed with an aqueous fluid, while on 
its lower surface is a layer of cellular tissue containing a similar sub- 
stance. Both are apparently destined for nourishing the feathers, or 
at least are connected with their growth. I have observed that at 
the period of moulting, and especially when the tail-quills are grow- 
ing, they are very highly developed, and, as is well known, some- 
times inflame and suppurate in domestic birds; whereas in birds in 
which the moult has been completed, I have generally found them 
greatly diminished, and frequently entirely shrunk. This fact, ana- 
logous to that of the periodical enlargement of the testicles in birds, 
affords a key to the knowledge of the nature and use of the uropy- 
gial gland which has hitherto eluded the sagacity of physiologists ; 
for the application of the oil contained in it by the bill is certainly 
fanciful.” 
I must express my surprise that such an accurate observer as the 
late Mr. Macgillivray should have confounded these glands with the 
cushion of fat in which the ends of the tail-feathers are imbedded: 
there is no resemblance in the structure of these bodies, and the use 
of the microscope would have decided the point at once. 
I have not observed that the tail-glands are larger at the time of 
moulting, although it is not unlikely, in consequence of a greater 
quantity of blood being distributed to the roots of the tail-feathers, 
that there may be a slight increase of bulk at this period, more espe- 
cially on the fatty portion of the tail. 
Montagu, Fleming, Bewick, Jenyns, Yarrell, and other writers on 
British Birds, I believe, do not mention these glands. I have not 
had time to consult foreign authors, but I assume that if any of these 
had described two glands, the circumstance would have been men- 
tioned by some English writers. 
It may be well to speak of the caudal appendage, or rather of its 
motor apparatus, before I proceed to the anatomical description of 
these organs. The tail of most birds, as is well known, is very move- 
able, and consequently requires powerful muscles to effect this mobi- 
lity. In the Peacock, and other gallinaceous birds with large tails, 
the rump-muscles are much developed, whilst in birds with small 
tails they are generally much diminished in size. The tail of a bird 
can be depressed, elevated, moved in a lateral direction, or the fea- 
thers can be spread out or contracted at the will of the animal. I 
need not describe minutely the origin and insertion of these muscles; 
it will be sufficient to indicate their general bearing. The elevator 
muscle (/evator coccygis)—a strong, powerful muscle in many birds 
—arises from the sacrum, from the bodies and sides of the coccygeal 
vertebrze, and is inserted into the spinous processes of these vertebree, 
and into the base and spinous process of the last vertebra. These 
muscles not only raise the tail, but when one acts, it moves it laterally. 
The antagonist to this muscle is the depressor of the tail (depressor 
