DISEASES OF THE HOG. 131 
PLETHORA. 
This is a morbid increase of blood beyond the 
wants of the system. It is not, however, a mere’ 
augmentation of volume in the circulating fluid 
that is entitled to this name. This may result from 
an excess of the watery ingredient and is not in- 
compatible with the state of the animal which is 
opposite to that of plethora. There must be a mor- 
bid increase of those constituents of the blood upon 
which its nutritive and stimulating properties de- 
pend and to which it owes its peculiar character, 
such as the red corpuscles, fibrin and albumen. 
There may or may not be any increase of bulk. It 
is not necessary that there should be an absolute 
increase of the blood in order to the existence of 
the disease. The quantity may remain precisely 
the same and yet if the wants of the system for the 
support of its various functions should diminish 
the phenomena of plethora may result; for it is the 
loss of balance between the supply and consump- 
tion, the former being in excess, that constitutes 
the affection. (Wood). 
Causes of Plethora: A loss of equilibrium be- 
tween the supplying and expending processes is 
the immediate cause of plethora. Digestion and 
absorption are relatively more vigorous than nu- 
trition and secretion. Thus feeding pigs more than 
they ought to be fed will produce this effect, espe- 
cially if the animal has little exercise. In some 
cases digestion and absorption may be healthy 
while nutrition and secretion may be in a deranged 
