PATHOLOGY 85 



General atrophy may be caused by lack of nutrition or ex- 

 cessive consumption and wastage of the soft tissues, especially 

 of the fats which are first taken ; as in typhoid fever in the 

 human body, or intiuenza in the horse. In this sense, general 

 atrophy is synonymous with emaciation. 



Degenerations and infiltrations.— These are characterized by 

 changes in the quality of a tissue ; the bulk may or may not 

 remain the same. In general when tissue degenerates, a cheaper 

 material is deposited in, and replaces tissue already diseased as 

 a rule. When infiltration occurs, the lower grade tissue is de- 

 posited between and later into the tissue elements, which at 

 the time are otherwise normal as a rule, e.g., the fat old house 

 dog or pet horse. The proper elements ma}' subsequently shrink. 

 In either case the affected organ loses in usefulness. The causes 

 of these degenerative changes are numerous, but they are closely 

 related, e.g., abnormal use or disuse, i.e., disturbance of function ; 

 heredity ; disturbance of nutrition, excess or deficiency, usually 

 the latter ; or certain poisons. No sharp line can be drawn be- 

 tween infiltration and degeneration. Possibly they should be 

 regarded as stages of the same process. 



Fatty degeneration is characterized by the development of 

 fatty matter in tissue cells, already diseased as a rule, and 

 replacing the proper tissue elements. This is especially 

 common in muscular and glandular tissue, e.g., heart and 

 liver. 



Fatty infiltration is characterized by a deposit of fatty matter 

 between the tissue elements and later in tissue cells. 



Calcareous degeneration and infiltration are marked by de- 

 posit of lime salts generally in tissues already diseased, as tuber- 

 culous lymph glands, and may be caused by any agency that 

 results in imperfect nutrition and lessened vitality. These con- 

 ditions occur more frequently in the tissues of older people or 

 animals. The muscular coat of the arteries sometimes becomes 

 calcified and brittle in old people and may even break under 

 unusual strain. 



Cells normally cartilage often deposit calcium, forming bone 

 as in the lateral cartilages of the horse's foot, causing lameness 

 and the unsoundness known as side bone. There are various 

 other degenerations and infiltrations besides these two named; 

 but in each case there occurs the deposit of some inferior tissue 

 into or between the proper elements of the organ. 



