BOG SPAVIN. 295 



The Magnitude and Form of the Tumour are, ordinarily, 

 that of the section of an orange, small or large, and prominent, 

 according to circumstances. 



The Site of the Tumour is the anterior and inner part of the 

 hock joint, in the interval between the malleolar projections of 

 the tibia, above and more anteriorly than the situation of (bone) 

 spavin. 



The Differences between Bog and Bone Spavins are, 

 therefore, obvious. Their sites are not the same. Their consist- 

 encies are different; one being soft, the other hard. And the 

 tumour of bog spavin is broad and extended, while that of bone 

 spavin is comparatively small, and is circumscribed. Other differ- 

 ences of a more important character there are, pathological and 

 consequential, which will become developed as we proceed. 



The Causes of Bog Spavin are such as produce windgall in 

 general ; to which may be added such as in a peculiar manner or 

 degree operate upon the hock. They may be regarded as divisi- 

 ble into general and local. Febrile, rheumatic, and general dropsi- 

 cal or oedematous affections, will be likely to be attended with 

 augmented secretion of synovia in the joints of the body in gene- 

 ral, and in an especial manner of the hock. But the hock being 

 the joint on which so much depends in progression, any excessive 

 work the animal may be made to perform, or excessive weight he 

 may be forced to carry, will in a peculiar degree tend to stretch, 

 strain, or disorder this joint ; so that, while the fetlock joints are 

 the parts upon which work or concussion tell in the fore limb, the 

 hock joints are the suffering parts, under like circumstances, in the 

 hind limbs. Considerations of the structure of the hock joint, of 

 its situation in the animal frame, of its motions and functions, will 

 satisfactorily account for its susceptibility to derangement and dis- 

 ease, as compared with other joints of the hind limb ; and we shall 

 pretty invariably find that its disorders are prevalent and intense, 

 according as the animal has been over-worked or over-weighted 

 at a tender age, or excessively worked or anywise abused in work 

 at an adult or advanced period of life. Intensity of motion, or 

 any undue stress upon the joint of the hock, tends to create irritation, 

 if not inflammation, in a part so delicate by nature as its lining 

 membrane, the consequence of which is augmented secretion of 



