SHEEP DISEASES : CAUSES, NATURE AND PREVENTION. 209 
changes, both structurally (histologically) and functionally (physi¬ 
ologically) ; thus, if water is deficient in quantity the blood be¬ 
comes thick, its plasticity is increased and, as a consequence, 
theie is a gieat tendency to stagnation (congestion). If water is 
superabundant, the colloids are held in an undue state of solution, 
the coloring matter is dissolved out of the red cells, and the walls 
of these little bodies may be actually broken up or disintegrated. 
Not only is this the case but, owing to the macerating process to 
which they are subjected, the white cells are injuriously acted 
upon, and the elements entering into the composition of the walls 
of the blood-vessels (particularly of the capillaries) become weak¬ 
ened and their vitality lowered, and they allow of the easy escape 
of serum into the tissues and cavities of the body, and thus we 
have produced dropsies (effusions). It is a well-known fact, too, 
that an excessive draught of cold water when the system is heated, 
will, particularly in man, determine an attack of nettle-rash solely 
by its effects on the blood and the glands \ and more than this, 
repletion and congestion of important organs is frequently pro¬ 
duced by similar causes. 
The colloids (proteids) of the blood are absolutely necessary, 
not only for the building up of the muscular and other tissues, 
but for their ordinary repair, as well as for the restoration and 
repair of tissues destroyed or damaged by disease and injury 5 
and any deficiency therein must be compensated—the compensa¬ 
tion taking place at the expense of the tissues. The colloids are 
rapidly disintegrated or used up in all important diseases, espe¬ 
cially fevers, hence the rapid emaciation (wasting) which is asso¬ 
ciated with and follows disease, and hence the value of giving 
albumen and fibrin in a readily assimilable form—as eggs and 
milk —in the treatment of fever. 
Excessive using up of the proteid elements, means not only 
emaciation, it means arrested growth, general debility, dropsy 
- and often permanent impairment of the general health; degraded 
proteids being passed out of the system as useless material by the 
kidneys and not again made use of. 
Great excess in these matters tends to the production of con¬ 
gestions and inflammations—produces, in fact, the so-called in¬ 
flammatory diathesis, or a tendency to inflammation. 
