ATKOPHY, DEGENERATION', PIGMENTATION, AND NECROSIS 87 



CALCAREOUS INFILTRATION. 



There is in this condition a deposition, either in cells or in the inter- 

 cellular substance, of larger and smaller granules composed chiefly of 

 phosphate and carbonate of calcium. These particles, when abundant, 

 give hardness, brittleness, and a whitish appearance to the affected tis- 

 sue. Under the microscope they appear dark by transmitted, white and 

 glistening by reflected, light. Tissues may be nearly completely per- 

 meated with salts, or the latter may be scattered in patches through 

 them. Sometimes large lamellated concretions are formed in tissues, 

 usually at the seat of some old inflammatory process. Calcification usu- 

 ally occurs in parts of tissues which are dead or are in a condition of 

 reduced vitality as a result of some antecedent abnormal process, as a rule 

 of an inflammatory nature. Among the most common and important 

 examples of calcareous degeneration may be mentioned those which occur 

 in the valves of the heart and walls of the blood-vessels. 1 



TECHNIQUE. The carbonate of lime deposited in the tissues is dissolved by dilute 

 acids with evolution of carbonic add gas. This process may be observed under the 

 microscope by running five-per-cent. hj'drochloric acid under the cover glass upon 

 unstained sections; the gas bubbles are caught as they evolve beneath the cover. 



Pigmentation. 



There is under normal conditions a certain amount of pigment in the 

 body in the rete Malpighi of the skin, in the eye, in muscle, and in 

 fat. This pigment is elaborated by the body cells and may vary consid- 

 erably in amount. 



The pigment which is formed under pathological conditions may be 

 derived from the blood honnatogenous ; from the bile hepatogenom ; or 

 it may be elaborated by various cells after the analogy of the normal 

 pigment metabolic. Finally, pigment may be introduced into the body 

 from without by drugs, in tattooing, or by inhalation. The pigment in 

 the body, of whatever origin, may be in yellow, brown, black, or reddish 

 granules, or in crystalline form. It is often deposited in cells, but may 

 lie free in the intercellular substance. 



HJEMATOGESOUS PIGMENT. Blood pigment may form by the decom- 

 position of haemoglobin in thrombi or in extravasated blood. Under 

 these conditions, the haemoglobin which is loosely associated with the 

 plasm of the red blood cells, readily diffuses, leaving the cells so-called 

 "blood shadows" pale and almost invisible and prone to disintegrate. 

 This destruction of blood cells is called hcemolysis. Haemoglobin in solu- 

 tion in the body fluids undergoes various phases of decomposition which 

 we cannot follow in detail here. One of the derivatives of the haemo- 

 globin is called JKfmosiderin. This pigment gives the micro-chemical re- 



1 Calculi are masses of solid material of various composition precipitated from thn 

 body fluids They will be considered under the separate organs in wliic'i they most 

 frequently occur. 



