EICKETS. 267 



body is unusually sensitive to pressure. This disease appears 

 to be caused by deficiency, in the food, of salts of lime, or of want 

 of power of assimilating such salts on account of the absence, in 

 the food, of other constituents which are necessary to healthy 

 digestion. Thus, Cheadle " cites a case of most extreme rickets 

 occurring in a child fed on skim milk, and also the beneficial 

 effect of cod liver oil. The cure of rickets in the lion cubs at 

 the Zoological Gardens, which were fed only on horse flesh, by 

 giving them cod liver oil and pounded bones with milk is a remark- 

 able instance of the part played by an improper diet in the produc- 

 tion of the disease. . . A deficiency of lime in the water of the 

 district has also been stated to be a cause of this disease, but 

 this is evidently not the case, for rickets is far more common in 

 London, which is supplied with water containing a considerable 

 amount of lime, than in Glasgow, where the water contains merely 

 a trace " (EricJisen). In human practice, the urine of rickety 

 patients sometimes has an excess of phosphate of lime, which is 

 derived from the imperfectly digested food, and not from the 

 rickety bones. Rickets is essentially a disease of youth ; as it is 

 connected with the deposition of new bone. 



The chief causes of rickets in the horse are a supply of milk 

 which is defective in quantity or quality; food which does not 

 furnish a sufficiency of salts of lime; too high feeding; and want 

 of exercise. All these causes may be intensified by insanitary con- 

 ditions. Hereditary infiuence in this disease seems to be confined 

 to the mare ; for no part appears to be taken by the sire. Although 

 it is probable that some foals, like some children, are born rickety ; 

 the exciting causes after birth are far more potent than those 

 before birth. On the Continent, foals not very infrequently get 

 rickets from being fed almost exclusively on bran, which, Tike 

 oats, contains much less mineral matter than hay. Roloff, Voit, 

 and others have proved by experiment that rickets can be pro- 

 duced by feeding young animals on food which is deficient in salts 

 of lime. 



Carnivorous animals are liable to rickets if they are fed on 

 meat without bones; and pigs, if their food consists almost en- 

 tirely of potatoes, which are poor in salts of lime. Rickets appears 

 to be less common on soils which are rich in lime, such as those 

 of chalk and limestone, than on soils poor in lime, like those of 

 gravel, sandstone, and granite. 



The swelling of the joints in rickets is caused by infiammation 

 set up, on account of the ligaments of the joints breaking away 

 from the soft bone to which they are attached. 



SYMPTOMS. — The first symptom to be generally noticed is 



