54 PATHOLOGY. 



atrophy and softening of the cornea, which melted down and 

 disappeared. Again, the stomach may be softened and its 

 mucous membrane dissolved by the action of the gastric juice. 

 This occurs in the dead body only, although it has been mistaken 

 for the effects of disease. Atrophy may also be caused by the 

 action of medicinal substances, such as mercury, iodine, bromine, 

 and the alkalies. Iodine and mercury are said to exercise an 

 influence on the lymphatic system, and bromine upon the 

 generative organs. Bone is sometimes atrophied both in the 

 horse and in the ox. This atrophy of bone is attended by a 

 diminution in its weight, but the size of the bones in the speci- 

 mens which I possess does not seem to be altered. The com- 

 pact tissue is thin, the cancelli have mostly disappeared, the 

 mediillary canal, filled with a lardaceous looking fat, extends from 

 one extremity of the bone to the other, and the periostial surface 

 of the bone presents a more or less cribriform appearance. 



The various structures of which an organ is composed may 

 suffer from atrophy. Some, however, do so more than others. 

 The fibrous tissue generally increases in amount. In glands, 

 the secretory cells are the first to suffer. They become small, 

 and often granular, from the presence of oil globules. In 

 muscles, the fasciculi become smaller, and lose their transverse 

 striae, and finally the whole contents of the sarcolemma may be 

 absorbed, and leave nothing but fibrous tissue, which may or may 

 not be transformed into fat. 



DEGENERATIONS OF TISSUE. 



The wellbeing of every part depends upon the nutritive pro- 

 cesses being actively performed by its cells, and upon a due 

 supply of properly constituted plasma — formative material, 

 germinal matter — protoplasm (Huxley), bioplasm (Beale) — 

 being conveyed to it by its vessels. The formative process — 

 nutrition — is performed by the cell, which is the seat of nutri- 

 tion and function, each individual cell being in itself an inde- 

 pendent organism, endowed with aU the properties of active life. 

 Various opinions are held as to the constitution of cells. Some 

 writers maintain that a cell is composed of a cell wall, enclosing 

 a cavity containing a nucleus and fluid contents (Schwann, 

 Eemak, Virchow, &c.) ; others state that the existence of a cell 



