CHAP. I.] MEMBRANES. ACUTE PAINS. 69 



where is the seat of poll- evil, it is usually thin, the 

 cavity there found between the bones being mostly 

 filled with muscle {section 21.) ; but this does not 

 happen invariably, as some horses have little or 

 no cavity to be filled with ligamentary substance, 

 or with muscle. Our frontispiece is the portrait 

 of a subject of this latter kind : but the reader is 

 referred to some subsequent observations and cases 

 on " poll-evil" for more detail on this hitherto- 

 neglected point of conformation. 



17. At the joints formed by the bones and 

 covered by cartilage, the whole are surrounded 

 by a strong membrane, which wraps the bones 

 tightly, and secretes an oil at the joint for its fur- 

 ther defence from the effects of friction. Of this 

 secretion, and of the membranes generally, some 

 further notice is taken in the second chapter, at 

 section 22 ; its absence constitutes Anchylous, or 

 stiff joint. 



This strong membrane is not, however, confined 

 to any particular part, but continues its close at- 

 tachment, or embracement of the bone, over the 

 entire frame of the horse, from the crown of his 

 head to the soles of his feet ; at the latter parts 

 protecting and further defending them from the 

 harder substance with which they are surrounded. 

 Throughout its extended course it serves as an ex- 

 cellent holdfast for the sinewy ends of the muscles 

 (see section 21.) which are attached to it above and 

 below joints, whereby they act as levers to raise the 

 lower bones of the limbs, as described hereafter. 



