248 V1■,T^;R1XAR^' pathcilocy. 



mentation of the skin in domestic animals, freckles are not easily 

 observed, except in white animals. 



Prcgmvicv in the human is frequently accompanied by local- 

 ized pigmented cutaneous areas. Such areas have n(Jt been re- 

 corded in domestic animals. 



Aside from the blnod, bile and cellular activities, pigments 

 ma^- be introduced into the body from without. 



The most common external substance that produces pigmen- 

 tation is carbon. The most extensive pigmentation by carbon 

 is in the lung, producing the condition known as anthracosis. 

 Anthracosis is a common condition in the lungs of animals used 

 in and around coal mines, in cities in which there is large quan- 

 tities of coal smoke, in cats and other pet animals confined in 

 cijal bins, engine houses, etc. The inhaled carbon is largely ex- 

 creted in the mucus discharged from the respiratory tract, al- 

 though some of it is deposited in the epithelium of the air cells, 

 and ultimatelv may be found in the interstitial tissue of the lung. 

 Anthracosis apparentU- produces little harm imless it is exces- 

 sive, when it prediijxises t(j inflammatory disturbances. AA'hen 

 examined in gross the lungs varv in color from a gray to a deep 

 black. Microscoiiicall)' small particles of carbon may be observed 

 in the cells and intercellular substances of the lung tissue. 



Argxriasis is a condition in wliich silver is de])osited in a tissue. 

 After the sih'er is deposited it is combined with sulphur, thus 

 forming silver sulphid, which is brciwnish black and imparts a 

 similar color to the tissue. Argyriasis is not common in animals 

 except those used in and around silver smelters or as a result of 

 the ai^plication of some silver preparation to the tissues. 



Sidivosis is a condition in which iron is deposited in a tissue. 

 Iron, like silver, usually combines with sulphur, forming the 

 sulphid, which is brown or black in color. Siderosis is not 

 common in domestic animals, except in the intestinal epithelium 

 of animals that liave Ijeen medicated with iron preparations. 



Hvdrargirosis is a condition resulting from the deposition of 

 mercury in a tissue. This condition is present in the intestinal 

 mucosa after medication with calomel or other mercury prepara- 

 tions. The mercury sulphid, wdiich is brown or black in color, 

 is the usual pigment in hvdrargirosis. 



Fliiinbosis is a term applied to pigmentation with lead. This 

 form of pigmentation may be evident in the intestine in chronic 

 lead poisoning. It appears as a bluish black ])igment. 



Tattooing is the introduction of insoluble pigments into tissues. 

 In tattooing, the tissues are first punctured or injured, after 

 which some insoluble pigment is introduced into the wounds. 



