ri-;tr()(;r1':ssivi-: tissi:!'; iiiancics. V)') 



parenchymatous tissue is most frequently involved, interstitial 

 tissue rarely becoming- atrophied. The diminution in size may 

 be uniform throughout, the atrophied part thus retaining its nnr- 

 mal shape, or the diminution may be unequal in different parts, 

 thus producing a lobulation of the affected portion. Atrophied 

 bone usually maintains its ncjrmal external sl-.ape, as the process 

 is essentially a rarefication in which the Haversian and medul- 

 lary canals are increased in size . rulmonar)' atrophy may con- 

 sist of diminution of the al\'ec)lar mem1)ranes to such an extent 

 that thev rupture, thus produciing large cax'ities. ;\trophic mus- 

 cular tissue is usualU- more intensely pigmented than normal 

 muscle. The source of the excess pigment in atrophic muscles 

 may be from the atrophied muscle cells or it may ha\e its origin 

 from the blood. 



jllicroscopic. — Tne cell bod}- and nucleus slirink in size in 

 simple atrophy without previous alteration in the cell structure. 

 In numerical atrophy the cells first diminish in size and then dis- 

 integrate and die. Thus atrophy, disintegration and necmsis are 

 evident in numerical atrophy. The appearance of atrophic tis- 

 sues vary according to the structures invuh-ed. Atrophic kidney 

 tissue is characterized by the diminution in the size or in the 

 nun-iber of the glomerular and tubular cells. The tubules and 

 glomeruli may collapse the supplying ca|iillaries liecuming oblit- 

 erated by pressure of the hyperplastic fibrous tissue. In muscu- 

 lar atrophv, the muscle cells diminish in size probably because 

 some of the fibrillae disappear. 



Effects. — The effect of atrophy depends upon the structure 

 involved the extent of the condition and the age of the animal. 

 If the involved structure is not vital and the atrophy is of only 

 slight extent and in a young animal, in which the regenerative 

 power is good, the part will recover if the cause is removed. 

 Extensive atrophy of vital structures in old animals is usually 

 fatal or at least predisposes to other conditions that are fatal. 

 Again, a part may partially recover after atrophic disturbances, 



