630 OPERATIONS ON THE FOOT. 



are picked up in the streets ; at other times it is a metallic sub- 

 stance elongated and sharpened ; again, there are pieces of glass, 

 or other substances, such as bones or sharp stones, which are 

 picked up and produce the wound. 



It is principally in the streets of populous cities, in the yards 

 of builders, or on the grounds where buildings are pulled down, 

 that horses are liable to receive these injuries. In rural districts 

 they are rare, comparatively, to what they are in cities. 



It is evident that horses with wide, flat, thin, softened hoofs 

 are more exposed than those which are of different structure. 



I. Divisions. — Punctured wounds of the foot may be simple 

 or superficial, deep g^ penetrating. 



One of these bodies piercLag into the frog requires to go in 

 deep to be serious, as above the frog (which is itself quite thick, 

 though formed by a soft and flexible horn) is the plantar cushion, 

 a fibrous, soft and elastic mass, which offers a great resistance. 

 If, however, the injuring body is a very long nail, which runs per- 

 pendicularly in through the frog at the plantar cushion, it may 

 reach the terminal extremity of the perforans tendon, situated 

 immediately under the plantar cushion, and penetrate the sesa- 

 moid sheath. It is known that this sheath forms a sac of some 

 dimensions, that it extends above and below from the inferior 

 half of the coronary to the semi-lunar crest, and in its transverse 

 axis extends from one retrosal process to the other ; the inferior 

 portion of this synovial bursa covers the plantar aponeurosis in 

 its whole extent. Sometimes, again, the puncturing body pene- 

 trates as far as -the bone ; sometimes the navicular ; at others the 

 OS pedis, and sometimes even penetrates into the articulation. 



II. Symptoms. — They vary according to the seat of the lesion, 

 its depth, the mode of action of the penetrating body, length of 

 time it has remained in the wound, and the nature of the lesions 

 it has made ; all conditions which may change the character of 

 the disease from a first degree, when the animal shows no evi- 

 dence of pain, to the extreme point, where its life is in danger, 

 and evens ends in death, by the excessive local alterations and 

 the sufferings accompanying it. 



Often the first point which assists in the' diagnosis of the case 

 is the history. The driver has seen the horse become suddenly 

 lame, has examined the foot, and found a nail more or less deeply 

 imbedded ; or it is the surgeon who finds the nail in its hiding- 



