Symptoms. The onset is absolutely insidious and the diagnosis of rachitis is never made until nutrition has long been abnormal.
This disturbance of nutrition is revealed by irregularity and abnormality in appetite, by difficulty in rising and moving about, and by the animals lying down for long periods. The subjects are feeble, sluggish and badly developed.
Next supervenes the second phase characterised by deformity of bones. This is of two kinds—deformity in the neighbourhood of joints (deformity or enlargement of the epiphyses) and deformity of the diaphyses. The former results from irregularity in ossification of the articular cartilages. The latter is followed by loss of rigidity in the bones of the limbs which, under the influence of the body weight and of muscular contraction, bend in different directions.
The bones appear of increased thickness principally towards the articulations. The latter are deformed, and on palpation are found to be surrounded by uneven and irregular growths.
The front limbs are distorted. In young pigs, lambs, and less frequently in foals, calves and dogs, the jaws become deformed, and mastication is rendered difficult.
The vertebral column may also be affected, and lordosis (bending downwards of the back) or skoliosis (lateral bending of the back) is somewhat frequent.
Cyphosis, or upward bending of the back, seldom occurs, and when seen, sometimes results from disease other than rachitis.
Fig. 1.—Rachitis in a young goat.
General development is always interfered with and the young creatures are generally dwarfed.