266 DISEASES OF BONE. 



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 infrequently get rickets 

 from being fed almost exclusively on bran, which, like oats, con- 

 tains m.uch_ l ess mineral matter than hay. It has been proved by 

 experiment that rickets can be produced by feeding young animals 

 on food deficient in salts of lime. 



Carnivorous animals are liable to rickets if fed on meat without 

 bones ; and pigs, if their food consists almost entirely of potatoes, 

 which are poor in salts of lime. Rickets_a,p,p_ear to be less co mmon 

 on soils which are rich in lime, such as thosie of chalk and lime- 

 stone, "than'ofi^ S'oils poor liiTihieTlTEe "tl5ose'oT~graveI7"sandstone, 

 ami'granite. ' " "" " 



The "Swelling of the joints in rickets is caused by inflammation 

 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 

 decrease in power of movement from one place to another, and 

 fatigue from comparatively slight exertion. There is gradual 

 swelling of the joints, chiefly of the hock, knee, and fetlock. The 

 animal may knuckle over in front and behind, or his hind fetlocks 

 descend down on the ground. In bad cases, the difliculty in 

 moving about gradually increases, until the animal is unable to 

 walk or even stand, and dies from want of food and exhaustion ; 

 there is a greater or less degree of paralysis of the limbs, which has 

 been shown by Bland Sutton (" Introduction to General Pathology ") 

 to be due to the gradual filling up, with spongy bone, of the spinal 

 canal, so that continued and increasing pressure is exerted on the 

 spinal cord, which, on that account, wastes away and becomes un- 

 able to properly stimulate the muscles of the limbs to exertion. 

 The bones of the spinal column (vertebrte), except those of the 

 tail, have a canal in them in which lies the spinal cord, and these 

 united canals form a passage (the spinal canal) which is continuous 

 with the cavity containing the brain. Thus, the spinal cord is a 

 continuation of the brain, and with it forms the great nervous 

 centre which, by means of the conducting nerves, receives im- 

 pressions from the various senses, and transmits stimuli to the 

 muscles. Continued pressure on nervous matter causes it to waste 

 away and lose its power of stimulating muscles to movement ; 

 paralysis being the result. 



In rickets the bones become so abnormally brittle that they are 

 apt to break with little or no unusual provocation. The curvature 

 of the bones of the limbs which is characteristic of rickets in 

 children, pigs, and dogs, for instance, is seldom well marked in 



