ALTERATION OF NERVE FIBRES AND CAPILLARIES, &C. 341 



give rise to products which cannot be readily ab- 

 sorbed, and which as they accumulate will seriously 

 interfere with the operations connected with nutri- 

 tion and impede the flow of nutrient fluid from the 

 blood to the adjacent tissues, as well as prevent the 

 return to the blood of the products of decay. We 

 see, then, that the structural alterations are conse- 

 quent upon changes occurring in bioplasm. The 

 bioplasm itself would not have been in the situation 

 indicated if the normal action of the capillaries, 

 arteries, and veins had been maintained and con- 

 trolled by the self-regulating mechanism which has 

 been described. 



The deterioration in structure of the coats of the 

 larger vessels is also due to an abnormal growth of 

 bioplasm, depending probably upon a previous change 

 in the composition of the nutrient fluid by which 

 their coats are permeated. 



The deposition of the so-called " atheromatous " 

 material in the wall of the artery is due to changes 

 consequent upon the presence of bioplasm in undue 

 proportion at a much earlier period. Bioplasts grow 

 and multiply in the substance of the arterial coats. 

 By the increase of these collections the layers of elastic 

 and muscular tissue are separated from one another. 

 In consequence the tissue deteriorates. After a time 

 the bioplasts die. Of the substances resulting from 

 their death some are absorbed, but others, such as the 

 fatty matter and calcareous salts remain behind and 

 accumulate, constituting the hard or soft matter 

 which is found in the substance of the arterial walls 

 in cases of very long-standing disease. Such are 

 some of the remarkable alterations which take place 

 in the walls of arteries, and not commonly precede 

 rupture and the occurrence of aneurismal dilatations 

 in the case of the largest vessels. Changes of the 

 same character affecting the smaller arteries and 

 capillaries invariably lead to serious derangement of 



