12 TRANSITION FROM HEALTH TO DISEASE. 



secretions and excretions are all products from the blood ; 

 and so long as they are equivalent to the chyle the blood 

 receives — so long the equilibrium is preserved, and plethora 

 warded off: abridge or interrupt these emissions, however, 

 and an effect similar to that which follows excess of nutri- 

 tion is produced. The secretions and excretions of the body 

 have not only the effect of giving vent to the redundance of the 

 circulating fluid — they likewise serve to purify it, by ridding 

 it of that which would prove noxious or insalubrious. This 

 operation of the animal economy, in conjunction with that 

 of the nervous influence, has led to the ingenious patho- 

 logical deduction framed by Dr. Copland : " That the in- 

 terruption or obstruction of any secreting or eliminating 

 function, if not compensated by the increased or modified 

 action of some other organs, vitiates the blood more or less ; 

 and if such vitiation be not soon removed by the restoration 

 of the function primarily affected, or by the increased 

 exercise of an analogous function, more important changes 

 are produced in the blood, unless the energies of life are 

 sufficient to repel the cause of disturbance, to oppose 

 the progress of change, and to excite actions of a salutary 

 tendency. ^^ 



Subjects of Plethora. — Young hors^ on their first 

 entry into stables, are the common subjects of the first de- 

 scription of plethora; old horses, or such as have become 

 habituated to stable-regimen, of the latter. No prudent 

 stable-keeper would feed his young or fresh horses high; 

 even while upon soft meat, such as mashes, &c. &c., it is 

 seldom that this state can be avoided. In those that are 

 not treated with necessary caution, it is a result almost 

 certain to happen. On the other hand, horses that are 

 habitually fed on stimulating diet, and whose work is 

 irregular, are subject to plethora, from the want of those 

 secretions being performed which require the active exercise 

 of body. Such is the case with a large class of those horses 

 that are kept for the purposes of pleasure. 



Forms of Plethora. — The effects of plethora appear 

 often to be warded off by natural processes going on in the 



