5S4 PATHOLOGICAL ANATOMY OF DOMESTIC BIRDS. 
A faulty or tardy developing of the feathers was observed in a 
young pigeon which, according to its age, ought to have been full 
feathered. The feathers were as if sealed in their horny sheath. 
Formation of Feathers in the abdominal cavity occurs; 
rarely, in the thorax. They aris&tmt of a peculiarly formed bag or 
sac, covered with fat; hence they were formerly considered as an 
abnormal accumulation of fat internally. They more particularly 
occur in waterfowl, principally in geese and ducks: if detrimental 
to the health of the bird, it can only occur through mechanical 
pressure on the viscera. These feathers are generally of stunted 
growth, seldom more than one or two inches long; commonly they 
do not protrude through the surrounding fat: sometimes these bags 
are suspended from a pedicle in the abdominal cavity. 
The horny structure is more or less subject to morbid alterations: 
the spurs in fowls, for instance, by their length or their direction, 
inconvenience or deprive the bird of his natural weapons of de¬ 
fence ; the beaks at times are apt to cross each other, so that the 
upper part has an opposite direction to the under part, which at all 
times must be a great inconvenience, often preventing the birds 
from taking their food. 
Insects, of the family philopteridce, are very troublesome to 
poultry, particularly to those which are sickly: however, they do 
not suck blood, like the pedunculce of the mammalia, but live on 
the feathers: nevertheless, they cause birds to be very restless, 
through their quick motions over the skin. Properly speaking, 
birds are never troubled with lice or fleas. The following genera 
are found on the different species of the farm-yard poultry:— 
On the peacock is found the goniodes rectangulatus, goniodes 
fallicornis. 
On the turkey, goniodes stylifer , leupeurus poly trapezius, meno- 
pon strumineum. 
On the guinea fowl, nicmas numidce, goniodes numidianus. 
On the common fowl, goniodes hologaster , goniodes disimilis, 
leupeurus variabilis, menopon pallidum. These are the worst 
of all, on account of the rapidity with which they multiply, and 
their easy transmission to the human subject. 
On the goose, nirmus tadornce (not ornithobius anseris , as has 
been incorrectly asserted), lipeurus jejunus, trinoton conspurcatum. 
On ducks, dolophorus icterodes, lipeurus squalidus. 
Two species of mites, acaridce , have been observed, viz. analges 
bifidus, which is found on the pigeon, does not suck blood, but 
feeds on the feathers; the dermanyssus avium, which is found on 
all birds, but more particularly on the common fowl and the 
pigeon, are very troublesome to the birds by night, since they suck 
the blood, on which they subsist: in the daytime they leave the 
