CORNS. 219 



upwards from the ground surface of the foot, is the region of the 

 navicular bone, which lies directly above the centre of the frog. 

 The navicular bone makes a joint with the pedal bone and short 

 pastern bone (Fig. 70), and forms a pulley for the perforans 

 tendon, between which and the navicular bone, a synovial bursa 

 is placed for lubricating purposes. Hence a puncture in this part 

 may wound the perforans tendon, the bursa, the navicular bone, 

 and the joint, and may extend even further up. Wounds towards 

 tlie point of the frog may cause fracture or chipping of the pedal 

 bone. Even without involvement of bone or tendon, very severe 

 inflammation may occur by puncture of the deep-seated sensitive 

 tissues of the frog (plantar cushion. Fig. 70) from the pus (matter), 

 which can hardy fail to form, not obtaining an efficient exit. In 

 all these serious cases, there will be great pain and high fever. 

 If the navicular bursa or joint be opened, there, will be a discharge 

 of synovia tinged with blood, which discharge will soon become 

 dark and stinking. 



Tetanus (p. 511) is not an infrequent result of wounds of the 

 sole and frog, which consequently should be treated antisepticaily, 

 so as to destroy, or, at least, to prevent the development of any of 

 the microbes of this disease that may be present. 



TREATMENT. — Remove any foreign bodies ; and treat as for 

 "Pricks in Shoeing" (p. 218). Moller's "Veterinary Surgery'' 

 contains a very able description of the operation necessary when 

 the perforans tendon has become diseased from puncture. 



PREVENTIVE MEASURES.— On no account thin the sole nr 

 pare the frog, except to remove loose or undermined parts ; and 

 allow the foot to retain its natural protection. Do not use " stop- 

 pings," which will make the sole and frog soft and spongy. 



Corns. 



DEFINITION. — A com is a bruise of the membrane which 

 secretes the homy sole and which covers the groimd surface of the 

 pedal bone. 



NATURE. — That portion of the sole which lies in the angle 

 formed by the wall and bars, and is called the " seat of corn " (Fig. 

 73), is the spot peculiarly liable to this injury, because the sole is 

 thinnest there ; the horse, in all his paces, places his heel first on 

 the ground; and the sensitive sole is apt to be pressed upon at 

 that part, by the horn of the wall, in the event of the heels being 

 allowed to grow too long, especially if the bars have been cut away. 



