DISRASES OF THE FETLOCK, ANKLE, AND FOOT. 443 



arrests evaporation and rapidly cools the external surface, thereby 

 determining an excess of blood to such organs and tissues as are pro- 

 tected from this outside influence. In many instances this happens 

 to be Some of the internal organs, as the lungs, if the previous work 

 has beeii rapid and their functional activity impaired; but in numer- 

 ous other instances the determination is toward the feet, and that it is 

 so depends upon two very palpable facts : First, that these tissues have 

 been greatly excited and are already receiving as much blood as they 

 can accommodate consistently with health ; second, even though these 

 tissues are classed with those of the surface, their protection from 

 atmospheric influences by means of the thick box of horn incasing 

 them renders them in this respect equivalent to internal organs. 



A more limited local actioil of cold may excite this disease, by driv- 

 ing through water or washing the feet and legs while the animal is 

 warm or just in from work. Here a very marked reaction takes place 

 in the surface tissues of the limbs, and passive congestion of the foot 

 results from an interference with the return flow of blood which is 

 being sent to these organs in excess. These are more liable to be 

 simple cases of congestion, soon to recover, yet they may become true 

 cases of laminitis. 



(5) Why it is that certain kinds of grain will cause laminitis does 

 not seem to be clearly understood. Certainly they possess no specific 

 action upon the laminae, for all animals are not alike affected ; neither 

 do they always produce these results in the same animal. -^ Some of 

 these feeds cause a strong tendency to indigestion, and the consequent 

 irritation of the alimentary canal may be so great as to warrant the 

 belief that the laminae are affected through sympathy. In other 

 instances there is no apparent interference with digestion nor evi- 

 dence of any irritation of the mucous membranes, yet the disease is in 

 some manner dependent upon the feed for its inception. Barley, 

 wheat, and sometimes corn are the grains most liable to cause this dis- 

 ease. With some horses there appears to be a particular suscepti- 

 bility to this influence of corn, and the use of this grain is followed by 

 inflammation of the feet, lasting from a few days to two weeks. 

 In these animals, to all appearances healthy, the com neither induces 

 colic, indigestion, nor purging, and apparently no irritation whatever 

 of the alimentary canal. 



(6) Fortunately purgative medicines rarely cause inflammation of 

 the laminae. That it. is, then, the result of sympathetic action is no 

 doubt more than hypothetical, for when there is no derangement of 

 the alimentary canal a dose of cathartic medicine will at times bring 

 on severe laminitis. 



(7) Almost all the older authorities were agreed that metastatic 

 laminitis is a reality. In my opinion metastatic laminitis is nothing 

 more nor less than concurrent laminitis, and presents little in any 



