268 DISEASES OF BONE. 



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 

 may descend down on the ground. In bad cases, the difficulty in 

 moving about gradually increases, until the animal is unable to 

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

 and 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 unable to properly stimulate the muscles of the limbs 

 to exertion. The bones of the spinal column (vertebrae), 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 impressions from the various senses, and transmits stimuli 

 to the muscles. Continued pressure on nervous matter causes it 

 to waste away and to 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 horses. In this disease, dentition is delayed in the 

 same manner as it is in osteoporosis (p. 262). The patient may 

 remain in good condition if fed in the ordinary way, even when 

 it cannot stand. Rickets runs a chronic course of several months. 



DISTINGUISHING SIGNS.— Rickets may be mistaken for rheu- 

 matoid arthritis, umbilical pyaemia (p. 532), or osteoporosis. The 

 swelling of the joints in rickets is of a far less inflammatory nature 

 and runs a much more chronic course than in umbilical pyaemia, 

 or in the rheumatoid arthritis of foals. The presence of pus in 

 the affected joints and constitutional disturbance are typical of 

 umbilical py[Temia. The peculiar swelling of the bones of the 

 face, the general progressive paralysis, and the absence of marked 

 joint troubles of the limbs separate osteoporosis from rickets. 



CHANCES OF RECOVERY from an attack of rickets are not 

 very hopeful ; for our equine patients have, as a rule, to be cured 

 sound; and not with the mere capacity of living. Rickety children 



