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coccygis), arising chiefly from the inferior and posterior part of the 
pelvis, from the bodies of the coccygeal vertebra, and inserted 
into their inferior spinous processes, and into the base of the last 
vertebra. The action of this muscle, single and double, is the reverse 
of the last-named. The quadratus coccygis arises from the lateral 
portions of the coccygeal vertebrze, and passes in a somewhat curved 
direction over the fatty prominence of the base of the tail, and is in- 
serted into the fascia below the tail, and into that enveloping the base 
of the tail-quills; it serves to spread and partly to raise the tail- 
uills. 
: The ischio-coccygeus arises from the ischium and lateral parts of 
the anterior coccygeal vertebra, and is inserted into the last vertebra 
and into the tail-fascia. It lowers the tail and moves it laterally. 
The pubi-coccygeus, on the under surface of the tail, arises from 
the posterior parts of the pubis and ischium, and is inserted into the 
fascia of the quills. It acts by spreading the quills and by moving 
the tail laterally. 
I have followed nearly the description of these muscles as given 
by Mr. Macgillivray, Professor Owen, and others. I could make 
many variations in the account when speaking of them in different 
birds, but this digression would be foreign to the object of my paper. 
I must, however, allude to two omissions made by these authors, 
which are important, I think, in relation to the function of the 
organs. ; 
In many birds a portion of the elevators of the tail is inserted into 
the base of the glands, so that when these muscles contract, they 
favour the escape of the secretion. But in other birds, the Moor 
Hen for example, a distinct pair of muscles is spread upon the pos- 
terior and inner portions of the glands, which they serve to compress, 
and thus assist in the ejection of their contents ; they also help to 
elevate the tail. 
I refrain from naming these muscles at present, as a long series of 
dissections will be required before the matter can be properly deter- 
mined, and the variations of these muscles accurately described. 
The above account may by some be thought unnecessarily prolix ; 
but I believe these muscles have an important bearing upon the use 
of the glands in question, serving by their action greatly to facilitate 
the passage of the oleaginous secretion. 
Form of the tail-glands.—These glands are of a rounded, oblong, 
flask-like shape, and would be well represented by the junction of 
two Florence flasks at their necks, their bases being somewhat widely 
separated. Inall the figures now exhibited of the six orders of birds, 
as will be seen, there is a general resemblance in their form. In 
some of the smaller passerine birds, however, they are more rounded 
than in the larger species. 
Situation.—In the great majority of birds which I have dissected, 
these glands have been found upon the levatores coccygis, having the 
quadrato-coceygei and pubi-coceygei on the outer side, the posterior 
part of the spine of the last caudal vertebra, and the same part of the 
two or three anterior to this, between them. In some birds, in the 
