ATKOPHY AND DEGENEEATIONS OF TISSUE. 61 



and are deposited in those portions of the tissues which imme- 

 diately surround the blood-vessels. 



Calcification is, however, a process most commonl/ dependent 

 on local causes — depending not upon any undue quantity of lime 

 salts in the blood, but upon a change in the part itself, whereby 

 the salts which are normally held in solution in the blood are 

 deposited in the tissues. Tliis process is often characterised as 

 an ossification, and not without some reason, as the so-called bone 

 cells or lacunse are often found in the calcareous substance ; they 

 are, however, imperfectly and irregularly developed. I have one 

 specimen in my possession, presented by Mr. Eobertson of Kelso, 

 where very well developed lacunse are found to exist in the cal- 

 careous mass. The specimen consists of a bony or calcareous 

 tube surrounding a piece of wood which had been lodged in 

 the inguinal region of a horse for some years. It is a most 

 perfect specimen of the ossification of an exudate, havmg no 

 connection with a bone. 



Calcareous degeneration seems generally to take place in parts 

 whose vitality has been lowered by previous morbid changes, 

 and in degenerating new formations. A part which has become 

 calcified undergoes no further change, bvit remains as an inert 

 mass : on this account it must be looked upon as a salutary 

 termination of a diseased process. It is thus the most favourable 

 termination to all degenerative diseases, as exemphfied in the 

 calcification of many new formations, inflammatory products, 

 tubercle, and atheroma of the arteries. 



Eindfleisch states that the cause of the deposition of the salts 

 in the substance of atrophied tissue is partly owing to the stag- 

 nation of the nutritive fluids in the part, owing to which the 

 free carbonic acid, which holds the salts in solution, escapes, in 

 consequence of which they are precipitated ; and partly to the 

 non-assimilation of these fluids by the degenerated tissue. The 

 saline matters are seen at first as fine molecules, scattered irregu- 

 larly through the intercellular substance, and are characterised, 

 when viewed by transmitted light, by their opacity, dark colour, 

 and irregidarity of outline. They are soluble in dilute mineral 

 acids, after which the original structure of the part, if not de- 

 stroyed by previous change, may again be recognised. 



Softening " consists in the liquefaction of the caseous substance, 

 probably owing to some chemical change in its constituents. It 



