538 DISEASES OF THE LIVER. 



blood, and also glycogen, into products that can easily be eliminated from 

 the system ; the waste material being finally excreted from the kidneys, in 

 the form, chiefly, of urea. The undue retention of these matters in the 

 blood, whether by the failure in action of the liver, or of the kidneys, gives 

 rise to great depression, and in extreme cases, to insensibility and death. 

 (4) To excrete carbonic acid. (5) To form bile. As the vessels which 

 supply the portal vein absorb nutritive matters from the food, it follows 

 that, when an animal is too highly fed, its liver will be unduly taxed, with 

 the result of more or less serious derangement. As the liver requires a 

 large amount of oxygen for the purification of, and changes wrought in, the 

 blood ; the want of air and exercise is specially injurious to that organ. 

 The rate of breathing directly affects the rapidity of the circulation of blood 

 through the liver ; hence, a state of idleness will tend to induce congestion 

 of that gland. The effect of a hot atmosphere not only diminishes the 

 amount of air taken into the lungs — for the warmer the air, the more 

 rarefied will it be — ^but, also, brings on destructive changes in the structure 

 of the liver. The skin, which is peculiarly active in the horse, helps the 

 liver in removing impurities from the blood ; hence, when the functions of 

 the skin are checked by the presence of a large proportion of moisture in 

 the air, the powers of the liver will be unduly strained. This fact appears 

 to be one of the chief reasons that hot, damp climates are peculiarly un- 

 suitable to horses. As exercise quickens the entire circulation, its absence 

 will, naturally, render that of the liver torpid. 



The liver is composed of a large number of lobules, which are about the 

 size of millet-seeds, and in which bile is manufactured. This yellow fluid 

 is carried from the lobules by bile-tubes, which unite, and finally form a 

 common duct, which discharges the bile and also the pancreatic juice into 

 the small intestine, in order that they may mingle with the semi-prepared 

 food (chyme) that has just quitted the stomach. The bile-tubes are lined 

 with mucous membrane, which, in a state of health, constantly secretes 

 mucus, to lubricate these passages. Surrounding this membrane, there is a 

 coat of involuntary muscular fibre which urges forwards the bile and mucus 

 by its contractions. 



Bile acts as a, natural purgative. Hence, when it is absent, the bowels 

 become constipated, and the dung emits an offensive odour and assumes a 

 clay colour on account of not being tinged by the colouring matter of the 

 bile. When the bile is regularly discharged, there are often ^ooffee-coloured 

 patches found on the dung ; a fact which is owing to an altered condition 

 of that secretion. Bile assists the pancreatic juice in forming an emulsion 

 with the fat contained in the chyme. These two fluids being alkaline, a 

 soap IS formed, in which the oily particles are split up into a very fine state 

 of division, so that the chyme (now called chyle) assumes a white appear- 

 ance. The object of the minute division of fat is to facilitate its absorption, 

 the fact of the mucous membrane of the intestines being moistened with 

 bile quickens the absorption, through this coat, of fat contained in the 

 food; hence, when the amount of the bile which is discharged into the 

 intestine is deficient in quantity, the animal will, in all likelihood, lose 

 condition. Bile also aids in the absorption of albuminous matters. 



Bile is composed of bile acids and colouring matter, which as we have 

 !?^"', is„,^erived from the colouring matter of the red corpuscles of the 

 blood. Ihe source of the bile acids has not been determined. 



When congestion of the liver occurs, its vessels become over-filled with 

 blood, and as, at the outset of every case of inflammation, the function of 

 the attacked organ is stimulated, an increased supply of bile is secreted 

 Ihe liver now swells considerably; the bile tubes become blocked up 

 owing to the inflamed state of their mucous lining, and to the presence of 

 the over-distended blood-vessels ; and the whole gland becomes gorged with 

 bile of which little or none, as shown by the clay colour of tie dune is 

 discharged. Ihe bile, thus obstructed, is in part absorbed by the blood 

 and taken mto the general circulation, so that the various tissues acquire 



