594 OPEBATIONS ON THE FOOT. 



membrane, and gives rise to an exhalation of the same nature as 

 that of the skin which produces the separation of the hoof, and 

 the first marks of canker. 



Sometimes one may observe at once, a fungoid growth of ficus, 

 formed by an hypertrophy of the tissues underneath ; this growth 

 is more or less moist and offensive, bleeding easily, having the 

 aspect of cauliflowers, and protruding through a break of the 

 softened hoof, and forming a thready detritus to be subsequently 

 studied. Commonly, the hoof is more or less loose, and under it 

 is a caseous matter, greasy, ordinarily of a fcetid odor, easUy re- 

 moved by scraping, being non-adherent to the tissue which 

 secretes it. If the parts are well cleaned from this, the velvety 

 tissue of the pyramidal body of the frog, appears to be covered 

 Tsdth a smooth membrane of a slight whitish color ; the external 

 layer then appears formed by a peUucid epidermic covering, show- 

 ing through its transparency the purpUsh color of the capUlaries 

 underneath. The velvety tissue is diseased, but still retains its 

 functions, which, on the contrary, are increased but perverted, 

 and instead of secreting a horny substance which adheres to the 

 surface of tbe keratogenous membrane, produces the caseous mat- 

 ter already referred to. The break in the hoof frequently seems 

 small in size. Nevertheless, the alteration of the keratogenous 

 tissues, viz : the substitution for its normal, of a pathological se- 

 cretion, whose product is this loose caseous matter, is far ad- 

 vanced. There is then an extensive, though a concealed separa- 

 tion of the hoof. One then must not aUow himself to be deceived 

 into supposing it to be a Hmited diseased process, by the apparent 

 external integrity of the horny box. 



The characteristic of canker is its tendency to spread, Hke can- 

 cerous affections. Once manifested in any part of the sub-homy 

 tissues, the special changes which characterize the disease seldom 

 remain circumscribed; on the contrary, they generally extend 

 from that part as a centre, throughout the whole circumference, 

 and little by little, attack slowly but continuously the whole ex- 

 tent of the secreting apparatus, and thus loosen the entire horny 

 box — starting from the median lacunae, or the glomes of the frog, 

 it extends to the branches and the body of the plantar cushion ; 

 then spreads at the side, in the lateral laminse, from there all round 

 on the velvety tissue, then by degrees reaches the inferior ex- 

 tremity of the podophyllous laminse and going upward, reaches 



