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CLINICAL DIAGNOSTICS. 



is best observed on the scleral conjunctiva. It is not noticeable 

 by artificial light. If the conjunctiva is pale (bloodless), the 

 yellow can be more readily appreciated. The shades vary 

 from a mere trace of yellow to pronounced lemon yellow ; in 

 most cases combined with congestion. The icteric discolora- 

 tion is due to the abnormal amount of bile coloring matter 

 found free in the blood serum. 



According to the origin of the yellow coloring matter we 

 distinguish : 



1. Hematogenous icterus originates from a dissolution 

 of the red blood corpuscles, the coloring matter becoming set 

 free and mixing with the blood serum. Hematogenous icterus 

 is really a hemoglobinemia. The dissolved blood coloring 

 matter (the methemoglobin) is not changed to bile pigment 

 in the blood, but in the liver. If this organ is able to convert 

 all of the coloring matter to bile and excrete it through the 

 bile ducts, the urine will contain no bile, but the feces will 

 become stained by it (hypcrcholia) and assume a dark color. 

 It may happen, however, that the bile becomes so thick that 

 it congests the smaller bile ducts, is reabsorbed and stains the 

 urine. 



Hematogenous icterus is seen in influenza of the horse, 

 azoturia, pyemia, septicemia [Texas fever], and in certain 

 cases of poisoning, especially after prolonged chloroform nar- 

 cosis. 



2. Hepatogenous icterus is due to the free flow of bile 

 from the liver becoming retarded (biliary stasis) and its pass- 

 ing over into the blood (cholemia) via lymph vessels and tho- 

 racic duct. The obstruction may have its seat in the biliary 

 capillaries or larger ducts, and often at the termination of the 

 ductus choledochus in the bowel. Hepatogenous icterus is 

 characterized by the appearance of bile pigments in the urine 

 while the feces, containing less than normal, are of too light 

 a color. 



