CHAPTEE VI. 



PATHOLOG Y— continued. 

 ATEOPHY A:N"D DEGENERATIONS OF TISSUE. 



ATROPHY, 



Atrophy implies a wasting of a part, arising from a diminu- 

 tion in the size or a decrease in tlie number of tlie tissue 

 elements of which that part is composed. Atrophy of the 

 normal structure of a part may take place without any apparent 

 diminution, but may be coincident even with an increase in size. 

 Thus, the fibres of a muscle may be atrophied, whilst its whole 

 bulk is increased by an interstitial exudation, which, pressing 

 upon the true sarcous elements, causes their wasting and absorp- 

 tion. Again, a glandular organ may be apparently enlarged, 

 whilst its true gland structures are considerably lessened. 



Atrophy is divided into simiile and numerical atrophy. Simple 

 atrophy is applied to the diminution in the size of the tissue 

 elements, and numerical atrophy to the process by which their 

 number is diminished. The two varieties are often associated. 

 Simple atrophy may, however, exist independently, but the 

 numerical never occurs without the simple. Atrophy is not 

 always a morbid process, as, for example, in the disappearance of 

 the thymus gland, which is large in the foetus, and is removed 

 shortly after the birth of the animal. 



Simple atrophy is well shown in ordinary emaciation, in which 

 fat disappears from the subcutaneous adipose tissue. Here 

 there is no destruction of the fat cells, but simply an absorj)tion 

 of some of their contents, by which their size becomes more or 

 less diminished. The same process may take place in the cells 

 of glandular organs, and so produce a dimiimtion in the size of 



