retr<)(;ressive tissue changes. 241 



frequently of secondary origin, the thickened bile forming the 

 nucleus. The results of inspissated bile depend first upon the 

 resorption of bile into the system and, second, upon the absence 

 of bile in the intestine. 



Inspissated Pus. — Empyema sometimes terminates, when 

 there is no surgical interference, in resorption of the liquor puris. 

 after which the solid ctjustituents frequently mass together, 

 forming concrements. These cuncrements may form in any cav- 

 ity in which the suppuration is slow going or chronic, provided 

 the movement of the part is limited. Their formation has been 

 noted in the guttural pouch. After formation thev may Ijccome 

 calcified. They are of little importance except as pathologic 

 phenomena. 



Lacteal concrements result from the coagulation of tlie casein 

 of milk and its accumulation in the galactophorous sinuses. 

 These concrements occur in the cow and can usually be expelled 

 through the lacteal duct by manipulation. 



Ceruminous concrementE occur in animals in which the hair 

 or wool extends far into the external auditory meatus. They 

 are composed of cerumen and are the result of an excessive pro- 

 duction or limited excretion of it. They may form into sufficient 

 masses to completely occlude the external auditory canal and 

 thus interfere with hearing. Concrements have been found m 

 the bronchial tulies. Their formation depends upon the accu- 

 mulation and condensation of mucus or purulent fluid. They 

 may obstruct bronchioles and produce atalectasis. 



Prostatic concrements frequentlv occur in old dogs. They 

 are present in manv of the enlarged prostate glands. The\- con- 

 sist of masses of accumulated colloid-like material. The results 

 depend upon the pressure that the}^ may exert. Thus there may 

 be an obstruction to the outflow of urine. 



PIGMENTARY CHANGES. 



Physiologic pigmentation is variable. The color and extent 

 of pigment varies in different animals and in the same animal 

 under different conditions. All physiologic pigmentation is the 

 result of deposition of hemogh.ibin or some of its derivatives. 



The skin of animals is usually extensively pigmented, with 

 the exception of albinos and some white skinned animals not 

 albinos. The production of the cutaneous pigment is not well 

 understood but probably results from metabolie activity of the 

 deeper layers of epidermal cells. Because of the intense cutan- 



