196 VETER1NAR\- PA'l IIOLOGY. 



enzyms, and hence is a factor in metabolism and in bringing 

 about retrogressive tissue changes. 



ranatioiis in tciii['cratiirs. — Tlie various albumens of protop- 

 lasm are coagulated at different temperatures. An increase of 3.6° 

 F. is sufficient to coagulate one group of albumins and an increase 

 of !J° F. is usually fatal because of the coagulation of other impor- 

 tant all)umin constituents of the cell protoplasm. Fever is invariably 

 accompanied by coagulation of some albuminous constituents 

 of protoplasm although it is possible that chemic substances as 

 well as the high temperature may ha\e some influence in this 

 coagulation. Diminished temperature retards metabdlic process- 

 es and if tissues are exposed for a sufficient time to a low tem- 

 perature the protoplasm dies and metabolism ceases. 



Diminished or increased cell ftnictionuuj are factors in the 

 causation of retrogressive changes. Diminished functioning for 

 a considerable length of time results in atrophy and if function- 

 ing of a specific part is decreased pr(_\gressively through several 

 generations there will be failure of development of that part 

 (aplasia). Excessi\e functioning, to a limited extent, in a 

 part supplied with an excess of food, produces hy|)ertrophy. 

 Functioning beyond the nutritive supply produces degeneration 

 and finally destruction of the cells. 



Retrogressive tissue changes include atrophy, degeneration, 

 infiltration and ])igmentation. 



ATROniY. 



DEFINITION. 

 DIFFERENTIA TfON. 

 KINDS. 



Pliysiologic. 

 Patholnqic. 

 ETIOLOGY. 



Physiologic. 

 Senility. 

 Pallioloiiic. 



Dishirbed nutrition. 

 Disturbed functinn. 

 Undue pressure. 

 APPEARANCE. 

 Macroscopic. 

 Microscopic. 

 TISSUE AFFECTED. 

 EFFECTS. 



Atrophy is that condition in which there is a decrease in the 

 size rif an organ or tissue caused by a decreased size or a dimin- 

 ished number of the composing cells. In some instance the 

 interstitial tissue increases and replaces the atrophied cells and 

 the affected organ does not diminish in size. The term atrophy 



