Atrophy. 189 



of the hard bone substance, the calcified lamell?e being Hterally 

 gnawed away by them. In addition muscle undergoing atroplT>' is 

 apt to show proliferation of the muscle nuclei, the sarcolemma 

 sheath often being full of nuclei and giving the impression of multi- 

 plication from lack of tissue pressure (lack of tissue tension) within 

 the empty sheath, as an associated phenomenon. This same ten- 

 dency to fill up spaces may also be observed in the fat cells, in 

 which, after the fat has been used up, there often accumulates a 

 watery or mucinous fluid, giving the adipose tissue a loose gelatin- 

 ous character (dropsical fat atrophy, often met in old horses in the 

 epicardium). Sometimes succeeding an atrophy in one tissue a 

 hypertrophy may take place in another, adjacent tissue; as when in 

 atrophy of muscular fibres the resulting space comes to be occupied 

 by proliferation of fat cells (atrophia miisculoruni lipoiuatosa). 



The deposition of the brownish pig-ment granules accompanying vari- 

 ous atrophies (muscle, heart, hver, ganghonic nervous cells) is as yet 

 not satisfactorily explained. [There is no doubt, however, that in most 

 cases at least, this pigment is of haemic derivation, although the substance 

 has been in some degree modified by cellular metabolism, and may there- 

 fore be spoken of as autochthonous in conformity with its usual classifi- 

 cation. It is a common feature of atrophic parts, as might well be expected, 

 both from the importance of poor blood circulation as a causative factor 

 and also from the diminished support afforded the capillary walls of 

 the wasted tissue, that some degree of passive hypera;niia should prevail; 

 and it may be noted that the degree of this pigmentary change is usually 

 in direct relation with the degree of such congestion.] 



Anatomically atrophic parts are usually characterized by dimin- 

 ution of volume, poor blood supply [poor circulation, not neces- 

 sarih- poverty of amount of blood present, however], loss of 

 their adipose tissue, by a tough, dry appearance and by the assump- 

 tion of a peculiar grayish tint sometimes approaching a brown .color. 

 The general bulk of the part may, however, be maintained by the 

 compensatory occupation of the space caused by the wasting of 

 its proper constituents by fat or connective tissue. Organs which, 

 because of their situation or the density of their peripheral structure, 

 are incapable of diminution may. however, manifest the presence 

 of atrophy by loss of weight, as the bones and lungs (osteoporosis 

 and emphysema'''). 



Atrophy invariably causes loss of function. Atrophic muscles 

 eventually are incapable of motion; glands secrete less efficiently; 

 bones become brittle: nervous structures lose their irritability and 



♦For details of these conditions c.f. Kitt. Lehrb. (J. patliol. Anatomie i?- 

 ffaustiere, II. Aufl., Enke. Stuttgfirt, 1902, 



