DISEASES OF THE FETLOCK, ANKLE, AND FOOT. 448 
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 been 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 aré 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 action 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 lamina, 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 laminz 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 corn neither induces 
colic, indigestion, nor purging, and apparently no irritation whatever 
of the alimentary canal. © 
(6) Fortunately purgative medicines rarely cause inflammation. of 
the lamine. 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 
