CIRCULATORY 'SYSTEM. 



123 



,<m 



f./-:^H.'-"; Hemaloblasls. 

 \~ '-^r* '' 



may be derived from their cytoplasm by a process 

 of budding or by particles merely breaking away. 



General Considerations. There is an old saying 

 that "a person is as old as his blood." A truer ex- 

 pression would be that he is as old as his blood- 

 vessels. With age, or dissipation, the blood-vessels 

 harden, due to depositions of connective-tissue ele- 

 ments. This impairs the free circulation of blood and 

 the body, as a whole, suffers. 

 The hardened condition is 

 spoken of as arteriosclerosis, 

 or atheroma. Usually the in- 

 tima suffers first by becoming 

 much thickened. Later, a 

 like disturbance takes place 

 in the media and adventitia. 

 As superficial scars remain 

 permanently, and can not be 

 eliminated, so there is no re- 

 lief for this scar formation of 

 the blood-vessels. Under this 

 hardened condition a rupture 

 of the smaller arteries is not 

 uncommon, particularly those 

 of the brain, as they have 

 thinner walls. Such a disas- 

 ter is apt to be fatal. 



An inflammation of the 



heart, as endocarditis, is apt to produce a deposit of 

 connective tissue in the endocardium, which upon 

 shrinking brings about defective valves, with leak- 

 age of blood. This increases the work of the heart, 

 and although that organ in an emergency can do 



Eosinophile. 



Marrow cell. 



Giant cell. 



Fig. 87. Cellular elements of 

 red marrow. 



