Pigmentation. 215 



high fever, indicate the existence of such an autointoxication, 

 which is designated as icterus gravis and cholcemia. 



Exogenous Pigmentation. — When the tissues are impregnated 

 with pigmentary substances which gain access to the body from 

 the exterior the process is known as exogenous pigmentation. 

 "The most common example is the deposition of carbonaceous ma- 

 terial (anthracosis) in the lung, practically always found in man 

 from inhalation of the particles ; it also occurs in dogs which 

 are compelled to pass much of their time in smoky places, 

 and in horses kept for a long time in coal mines. The in- 

 haled dust, except that which is removed by the bronchial 

 mucus and by the ciliary activity of the tracheal cells, re- 

 mains suspended in the alveoli [and smaller tubes], is taken up 

 by wandering cells (dust cells) : part being carried in 

 the pulmonary lymph channels and reaching the lymph glands 

 of the lungs and bronchial tree, part being deposited in the lymph 

 spaces of the lungs. Wirying with the quantity of carbon thus 

 deposited, the lungs and lymph glands become mottled and of a 

 grav slaty appearance or uniformly and completely blackened.* 



Dark pigmentations may also be caused by the deposition of 

 mercurv, lead and silver, observed som.etimes after medicinal 

 administration of preparations of these metals, as in case of the 

 black color of the intestinal villi in the horse after the adminis- 

 tration of calomel. It is usually the result of the formation of 

 mercuric and plumbic sulphides from contact with the sulphuretted 

 hydrogen of the gastro-intestinal contents. In employing nitrate 

 of silver in internal medication it is absorbed from the alimentary 

 tract and deposited in extremely fine granules (reduced to metallic 

 silver) in all the different organs, skin, conjunctiva, kidneys, etc., 

 and gives them a grayish pigmentation. The condition is known 

 as argyria. 



By means of subcutaneous and intravenous injections of staining 

 solutions (carmine, indigo-carmine, methylene blue) the tissues of the body 

 may be colored bUie or red. The protoplasm of many cells takes up the 

 stain diffusely in part ; sometimes instead a granular deposition takes place 

 from combination of the piginent with certain granular constituents of the 

 cells (Arnold, Ribbert). 



[The eff'ect of external or exogenous pigmentation is usually 

 trivial aside from the mere discoloration and is only important 

 when intense or as a predisposing cause to more serious dis- 



*For details cf. Path. Anatomie d. Haustiere. II. Aufl. Stuttgart, Ferd. Enke. 



