LECTURE XV. 



questionably the most widely spread and the most im- 

 portant in the course of all cellular disturbances, is fatty 

 metamorphosis, or as it has also long been wont to be 

 called, fatty degeneration. This process is attended by a 

 continually increasing accumulation of fat in different 

 organs. Even the old notion of fatty degeneration in- 

 volved the idea of a continually increasing change of such 

 a nature that pure fat at last took the place of whole 

 parts of organs. It has turned out, however, that this 

 old notion', which is even now retained by many in the 

 language of pathology, includes a great number of com- 

 pletely different processes, and that errors would inevit- 

 ably be committed if it were sought to interpret the whole 

 group from a pathogenical point of view, in a simple 



manner. 



The history of fat in its relation to the tissues may, gene- 

 rally speaking, be considered under three aspects. We 

 find namely one class of tissues in the body, which serve 

 as physiological reservoirs for fat, and in which the fat is 

 contained as a kind of necessary appurtenance, without 

 however their own permanency being in any way en- 

 dangered by its presence. On the contrary, we are actu- 

 ally accustomed to estimate the well-being of an indivi- 

 dual by the amount of fat contained in certain tissues, 

 and to regard the degree of fulness presented by the in- 

 dividual fat-cells as a criterion of the successful progress 

 of the interchange of matter generally. This forms there- 

 fore a complete contrast to the necrobiotic processes, m 

 which the part, in consequence of the accumulation of fat, 

 really altogether ceases to exist. 



A second series of tissues do not constitute regular re- 

 servoirs for fat, on the contrary fat is found in them only 

 at certain times and transitorily, for after a short time n 

 again disappears from them, without their being on that 

 account left in an altered state. This is the case m the 



