70 PATHOLOGY OF SPAVIN. 



on this introductory part of our subject. The joints of the hock 

 and knee — unlike joints in general, which are composed of two, or, 

 at most, of three bones — are constituted, respectively, of several 

 bones, having articulations between them, which, besides being 

 for tlie purposes of motion, are made useful in counteracting con- 

 cussion. There are no less than ten bones, and nearly as many 

 joints or articulations, concerned in the composition of the hock ; 

 though but two of the bones, with the joint they form between 

 them, are absolutely necessary for flexion and extension. The 

 other smaller articulations, though contributing to motion, being 

 especially serviceable in diverting or warding off concussion from 

 the principal joint — that between the tibia and astragalus. In 

 particular, the large and middle cuneiform bones, and the small 

 metatarsals, are concerned in this latter function : hence it is, that 

 these are the structures which — as we shall discover hereafter — are 

 especially subject to disease. Concussion, however, operates 

 differently in one instance from what it does in the other. Any 

 force or shock received by the cuneiform or cushion bones is 

 transmitted at once upon the large metatarsal bone, and along it 

 conveyed to the pastern, and thence to the foot ; whereas, pressure 

 made upon the small metatarsal bones is received by the elastic 

 fibro-cartilaginous substance uniting them to the large bone, they 

 having no bony supporters. In the one case, therefore, concussion 

 would operate upon the bones themselves, in the other, upon 

 a soft inter-osseous substance : consequently, the articulating 

 surfaces — their synovial membranes and articular cartilages — 

 would be the parts to suffer in the cuneiform bones; the inter- 

 osseous fibro-cartilaginous attachments, the parts to fail in the small 

 metatarsal bones. Leaving the former for consideration hereafter, 

 I shall at present devote my attention to the metatarsal joints. 



Professor Coleman's opinion was, that spavin originated 

 in splent of the hind leg. His words, in his Lecture on the sub- 

 ject, are, " The nature of spavin is, that the substance which con- 

 nects the small to the large metatarsal bone, being violently put on 

 the stretch (for it is highly elastic), inflames; and the result of 

 this inflammation generally is, that ossific matter is effused, and 

 becomes the medium of connexion between these bones. The 



