284 PATHOLOGY OF NUTRITION. 



Ha3matoidin is found in rhombic crystals or granular in old 

 blood-clots, free or within leukocytes and other cells. 



b. Of non-hsematogenous pigments, melanin is the most 

 important. It is elaborated by living cells, and contains no 

 iron. Granules of melanin vary in color from yellow to black. 

 It is noted, among other instances, in melanotic sarcoma (Fig. 

 116). 



2. Extrinsic : Extrinsic sources of pigment are very numer- 

 ous, the material being absorbed either through the lungs or 

 gastro-intestinal tract. Carbon is one of the most common 

 varieties of extrinsic pigment. When coal-dust is inhaled it 

 gives rise to deposits of pigment in the lungs, the condition 

 being known as coal-miners' lung, or anthracosis (Fig. 117). 

 Siderosis is similarly produced by the inhalation of fine parti- 

 cles of iron, the lungs becoming rusty in color. In chalicosis, 

 stonemasons 7 lung, the particles are white and the lung con- 

 sequently abnormally pale. 



In argyria silver is absorbed from the gastro-intestinal 

 tract and afterward deposited in the tissues as an albuminate. 

 The condition was more often seen when silver was popular 

 in the treatment of epilepsy and other diseases of the nervous 

 system. 



Atrophy. 



The term atrophy means literally want of food. The af- 

 fected organ undergoes a more or less uniform reduction in size 

 and weight. It may be congenital agenesia or acquired. 

 In true atrophy there is a decrease only in the size of the cells 

 of the tissue, their number remaining normal. A decrease in 

 the number of cells is sometimes spoken of as aplasia, or 

 more generally as numerical atrophy. Hypoplasia is a failure 

 of the cells to reach their natural size. 



The condition is seen physiologically in the thy m us gland 

 in the second year of life, in the generative organs at the 

 climacteric, and in the general atrophy of old age. 



Pathologically deficient blood-supply, if long enough con- 

 tinned but not too severe, is an important cause. Under this 

 head would come pressure-atrophy, e. g., the absorption of 

 the bodies of dorsal vertebrae by an aortic aneurism and 



