110     THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, I

DISCUSSION. The condition described above should be differentiated from
scaly leg and productive inflammation of the soft structures of the shank of fowls,
which also develop without any signs of acute inflammation. The shank, in the
latter affection, gradually becomes larger due to newly formed connective tissue,
but the increasing enlargement is limited to the soft structures alone, the bony
tissue not being involved. A skiagram will reveal its true nature.

The condition of chronic osteitis may either be a sequel of certain constitutional
disturbances such as " Osteitis deformans " or ' rickets ', or it may result from
chronic bacterial infections such as tuberculosis, actinomycosis and gummatous
osteitis.

As regards the causation of Osteitis deformans in man, various theories have
been proposed and many infectious agents have been held responsible including
the organism of syphilis. It was held, by some, to be due to the effect of the
disturbance of some internal secretion. There appears to be little evidence in
support of these views. MacCallum [1924] refers to this condition as " Paget's
disease " and, in 1876, he described it in human beings as affecting the bones of
the extremities and the skull. It is further observed that the changes in some
cases may be unilateral or may be limited to one or two bones. The condition
progresses slowly with some tenderness and pain in the altered bones. The marrow
loses its blood forming elements and becomes converted into a vascular fibrous
tissue which produces much soft bone-like tissue ; the marrow cavity is encroached
upon and filled completely. The softened bone later assumes an ivory-like
hardness. So Paget inclines to the view that the process is of an inflammatory
nature, resulting in enlargement and excessive production of imperfectly developed
osseous tissue which becomes organised.

MacCallum [1924] in dealing with gummatous osteitis, describes a form in
which the new production of bone is more extensive than in the periosteal type
and states that it is deposited in each Haversian system and through the cancellous
bone in the interior so that the shaft of the bone becomes dense and ivory-like
and the whole bone is much heavier than normal.

Kaupp [1933] has described the condition of ' Osteitis deformans ' as occurring
in fowls and observes that Goldman has described a case in fowls affecting the
front part of the skull and the long bones, including the femur, humerus and
metatarsus. Many have held that rickets, osteomalacia and osteitis deformans
are manifestations of the same disease bearing on impaired nutrition and deranged
matabolism. It is supposed that, in the course of calcification, a certain amount
of the sulphur of the matrix is replaced by other elements, which must entail the
retention of calcium, magnesium and phosphorus and involve the increased elimi-
nation of sulphur.

Kaupp states that DaCosta and his co-workers interpret the retention of
calcium, magnesium and phosphorus with excessive excretion of sulphur found