Hereditary Diseases of Horses. 



115 



and consequently their predisposing* causes are easily traced, and 

 usually consist in some peculiarity of external form more or less 

 obvious. This observation chiefly applies to several sorts of lame- 

 ness, which we shall now notice. 



Bone Spavin consists in inflammation of the ligamentous and 

 synovial connections of the bones of the hock, and usually of those 

 between the cuneiform medium and metatarsal bone. Effusion 

 occurs, forming an exostosis or bony tumour on the antero-internal 

 part of the hock, attended during its formation with great pain and 

 consequent lameness. Violent and continued exertion, especially 

 when the animal is growing, is the usual immediate cause of this 

 disease. The amount of strain of the parts affected, and the con- 

 sequent liability to the disease, are always greatest where the 

 width and strength of the limb below the hock are disproportioned 

 to its width and strength above the hock. Horses of such con- 

 formation are unusually predisposed to the most troublesome 

 and serious cases of spavin, and hand down to their progeny a 

 similar conformation and predisposition. Other bony deposits 

 besides spavins are also more apt to affect some families than 

 others. This tendency may depend on an endeavour on the part 

 of nature to strengthen a local weakness, as well as on a general 

 disposition to the formation of exostosis — a disposition always 

 more frequent and stronger in the horse than in most other 

 animals. 



Curb is a strain of the calcaneo-cuboid, or posterior straight 

 ligament of the hock, causing pain and swelling on the postero- 

 internal part of the joint. Horses most subject to it are those in 

 which the hock is straight and the os calcis short and inclining 

 forwards. 



Of all the complaints to which horses are liable there is none 

 more frequent, more troublesome, or more tedious than strain of 

 the hack tendons. It usually consists in rupture of the minute 

 fibres of the tendo perforans, or of the strong check ligament at- 

 tached to it. To repair this injury inflammation is established; 

 effusion soon follows, and occasionally thickening and shortening 

 of the limb. The frequency and severity of this accident might 

 be greatly diminished by breeding only from animals with sound 

 well-formed limbs. The chances of its occurrence are least in 

 horses having well-shaped knees, sufliciently large both in their 

 anterior and lateral aspects, with the tendons prominent from the 

 fetlock upwards— a formation which gives a flat appearance to 

 the limb when viewed from the side. Horses, on the other hand, 

 with round legs and small knees, to which the tendons are tightly 

 bound down, are especially subject to strains, on account of the 

 want of that full prominence of the posterior part of the knee 

 which is found in limbs of a more perfect conformation, and 



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