Grease. Seborrhcea of the Digital Region. 513 



horse, being rare in racers and trotters, with fine sinew}' limbs, 

 no long hair on the fetlock, delicate skins, and less abundant 

 sebaceous glands. It is almost, though not quite, unknown in the 

 spare limbs of ass and mule, and though claimed by Reynal as 

 attacking cattle its occurrence is equally rare in them. Much of 

 this may be attributed to conformation. The liml) of the draught 

 horse is so much thicker and coarser, with a great excess of con- 

 nective tissue and lymph plexus which become readily gorged in 

 idleness, inducing stocking, congestion and debility of the whole 

 limb. This same condition operates as a powerful predisposition to 

 lymphangitis. Again the great length and profusion of the long 

 hairs, entails the necessary compliment of an excessive development 

 of the sebaceous glands which become over-stimulated by conges- 

 tion, and afford a much more open and favorable infection atrium for 

 the pus microbes. These structural conditions are much more 

 marked in the draught horses of wet regions as in Ireland, the 

 western counties of Great Britian, Belgium, Holland, and the At- 

 lantic provinces of France, and in these the affection is remarkably 

 prevalent. In our Eastern vStates and on the Plains, where the 

 progeny of imported draught horses lose their digital hair, the 

 malady is comparatively rare. A similar immunity has long been 

 noticed in the horses of Spain and Africa. Disturbances of the 

 digestion in heavily fed horses, subjected to transient confinement 

 in the .stall, and diseases of the liver and kidneys, must be recog- 

 nized as further predisposing causes. The age of five and six 

 when many horses change hands, and are subjected to extreme 

 changes of .stabling, feed and work, has furnished the greatest 

 number of cases. 



External causes we find in all those conditions already 

 enumerated which favor chapped heels. Wet, mud, gritty 

 masses, irritant fumes of manure, cold, heat, filth are potent 

 factors. In connection with these are the pus and septic microbes 

 that are always present in stables, farm yards, manure, street 

 dust, etc. No one of these can be adduced as the constant and 

 exclusive cau.se, and it is inevitable that a complex infection 

 should be present, yet the propagation and persistence of the 

 disease may often be connected with the streptococcus pyogenes. 



As emphasizing the importance of such external irritants and 

 infections, it should be noted that the disease bears an appreciable 

 33 



