DISEASES OE THE STOMACH AND INTESTINES. 641 
fluid, as the greater part of the contractile force is obviously 
exerted upon the empty space before the fluid can be reached 
at all. A defective circulation, or even an entire suspension 
of the process, is easily explained by the simple fact of a 
sufficient amount of fluid to be influenced by the com¬ 
mencing contraction. Besides this, however, we may esti¬ 
mate as of considerable importance the absence of the dis¬ 
tending force, which doubtless has much to do with the pri¬ 
mary excitation of the functions of contractile tubes. 
Debility, we cannot fail to perceive, is the inevitable con¬ 
sequence of any conditions of the organism which lead to 
diminution of the volume of the circulating fluid. In this 
way, diarrhoea being associated with the secretion of a large 
amount of the water of the blood in association with albumen 
in small quantities, and a considerable proportion of the 
saline constituents, causes an impaired circulation, by de¬ 
creasing the bulk of the blood so much that the impelling 
force is wasted upon space, while the fluid remaining is so 
viscid, from deficiency of water and salts, that it would 
require more than ordinary energy in the circulatory system 
to ensure its equable distribution. 
Another characteristic of diarrhoea is the altered condition 
of the evacuations, not only in quantity and consistence, but 
also in composition and colour, varying, as they do, from 
white to black. 
The explanation of this fact is usually to be found in the 
nature of the food, or otherwise in the amount of the 
colouring matter of the bile secreted during the diseased 
action. In very young animals, living upon milk, the white 
dejections are consequent upon imperfect digestion of this 
fluid, and its premature expulsion from the stomach and 
intestines. When the food consists principally of herbage, 
similar derangement of function results in the evacuation of 
green feculent matter. Deficiency of biliary colouring will 
occasion a clay tint, while excess of it produces sometimes a 
perfectly black colour. 
The composition of the evacuations will obviously depend 
upon the contents of the alimentary tube, but after a certain 
time the major part of the solid matter is removed, and 
nothing but the serous fluid, discoloured by washing over 
the intestinal membrane, and commingled with a little mucus, 
remains to be expelled. 
General derangement of the secretions is another con¬ 
dition of the disease, not by any means remarkable when we 
consider the effects which must follow from the diminished 
volume and deteriorated state of the blood: thus dry and 
xxxv. 41 
