Fig. 4.—Deformity of the face in the horse shown in Fig. 2.
The flat bones are particularly liable to this change, which is common to domesticated animals. The bones of the head are the first to suffer; later those of the pelvis. The lower jaw becomes swollen, particularly about the centre of the branches which may attain three, four, or five times, their normal thickness.
The depression in the submaxillary space disappears. The upper jaw undergoes similar changes, becoming deformed and thickened until the cavities of the sinuses and the hollow appearance of the palate are lost, while the face is so changed that it cannot be recognised as that of a horse, goat, etc.
The molar teeth are almost buried, their tables alone being visible at the bottom of a depression, the edges of which rise above the neighbouring parts (pig).
Mastication is clearly impossible, the jaws appear paralysed, the muscles powerless, and only swallowing is possible, a fact which explains why life is only prolonged to this stage in animals which can be fed with a spoon or bottle (pigs and goats). The bones of the cranium, although greatly changed in texture, are always less deformed than those of the face.
The changes are such that it is often easy with a mere post-mortem knife to cut the head completely in two. Osseous tissue, properly so-called, has disappeared.
All the constituent tissues, with the exception of the skin and muscles, i.e., the bone, periosteum and aponeuroses, have the appearance and consistence on section of the fibro-lardaceous tissue seen in chronic inflammation.
The following is a condensed description of the disease as given by Law:—
Symptoms. Poor condition or even emaciation, with very visible projection of the bones. The coat is rough, skin tense, inelastic and hidebound, appetite variable, sometimes impaired, and nearly always perverted (or depraved) so that the patient will lick the manger continually or pick up and chew all sorts of objects: bones, leather, clothing, wood or iron, stones, etc. The amount of food consumed may, however, be up to the normal. The most marked feature is the difficulty and stiffness of locomotion.... Temperature and yield of milk may remain normal.