RACHITIS. 5 



equipped for their future development. Their tissues lack the necessary 

 qualities and, c ceteris pavihus, their physiological functions are performed 

 less perfectly than are those of normal individuals. 



It is difficult to apply such information to domestic animals, because 

 badly developed subjects are not used for reproduction and the import- 

 ance assigned to heredity can therefore scarcely be sustained. The 

 conditions of life, on the contrary, have an unquestionable influence, 

 and if rachitis is so frequent in young animals living near towns, for 

 example, it is undoubtedly due to that want of air, light and liberty, 

 which first affects the mother's health and later that of her offspring. 



The same may be said of insufficient and improper food ; for in this 

 connection quality is of even greater importance than quantity. Even 

 free feeding is insufficient if the fodder does not contain the material 

 necessary for sustaining and building up the developing frame, a point 

 which readily explains the occurrence of rachitis when young animals 

 receive a diet deficient in certain chemical constituents. 



This occurs in young lambs and pigs where the mothers are given too 

 little variety or too small a quantity of food. 



In calves and foals rachitis is rare but occurs when the mothers are 

 exhausted or cachectic or are debilitated by chronic wasting diseases like 

 tuberculosis or osseous cachexia. The milk is then no longer of normal 

 chemical constitution. 



One fact appears to dominate the whole subject of the causation of 

 rachitis, viz., the failure to assimilate sufficient of the mineral salts 

 required in building up the skeleton. This failure to assimilate may be 

 caused by too meagre feeding, but even when the food is sufficiently rich, 

 some digestive disturbance may reduce the amount absorbed below 

 normal. This appears the only plausible explanation unless we admit Dr. 

 Chaumier's theory that the disease is of an infectious character. 



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 abnor- 

 mality 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 



