474 Veterinary Medicine. 



etc. , tend to induce indigestions and to lay the bile ducts open to 

 infection. Blocking of the bile duct and stasis oi its contents 

 may be a sufficient cause. The swollen mucosa around the orifice 

 of the duct not only blocks the passage but favors the formation 

 of a mucous plug as recorded by Benjamin of an equine patient. 

 Wolff found obstructions of the duodenum in the horse by a mass 

 of ingesta, and blocking of the gall duct, with jaundice. 



Gall stones and concretions are very direct causes of biliary ob- 

 struction and jaundice. Though less common in horses than 

 cattle, these are not unknown in idle, pampered animals when on 

 dry winter feeding. 



Tumors of the pancreas or adjacent organs pressing on the gall 

 duct are recognized as causes of equine icterus, (Megnin, Nocard), 



With any obstruction to the bile a disturbance of balance of 

 pressure between the bile ducts and the hepatic veins is brought 

 about by respiratory movements. On the one hand the aspira- 

 tory power of the chest empties the hepatic veins, lessening blood 

 pressure, and in expiration the contraction of diaphragm and 

 abdominal muscles compresses the gall ducts increasing their 

 tension and favoring absorption of bile. 



The entrance into the bile duct of the ascaris megalocephala is 

 at once a cause of obstruction and of the transference of duodenal 

 microbes, and the presence of trematodes (fasciola hepatica, or 

 distoma lauceolatum) will also favor obstruction. Other para- 

 sites, like the echinococcus or actinomycosis, may press on the 

 bilary ducts and determine jaundice. 



Another mode of infection is by way of the portal vein, the 

 microbes entering from the intestine and becoming arrested and 

 colonized in the liver (Dieckerhoff). 



Whether from the presence of the microbes or from the absorp- 

 tion of ptomaines and toxins from the intestines, the radical 

 biliary ducts become inflamed, swollen, and even blocked, and 

 the hepatic cells degenerated or even completely devitalized, so 

 that they fail to take an aniline stain. In such cases the remain- 

 ing sound hepatic cells go on producing bile, but as this cannot 

 any longer escape through the partially obstructed interlobular 

 biliary radicles, it is largely absorbed and produces icterus. 

 Cadeac mentions a case of this kind in a mare in which the toxic 

 matters had not only led to hepatic disease, but also to structural 

 changes in the eliminating organ (the kidney). 



