420 BIOLOGY: GENERAL AND MEDICAL 



mentation of the cells of the seminiferous tubules and 

 the formation of spermatozoa almost ceases. The pros- 

 tate gland sometimes enlarges in old men, but in not a 

 few aged men follows the usual rule and atrophies. 



The blood-vascular system undergoes a general fibrosis, 

 chiefly characterized by loss of muscular and elastic 

 tissue. The endarterium is prone to suffer from pro- 

 liferation of the subendothelial tissues and more or less 

 obstruction. These changes may be accompanied by 

 more or less saponaceous change followed by calcifica- 

 tion. If calcification chiefly localizes in the middle 

 coat, the vessels may be transformed to mineralized 

 hollow cylinders " pipe-stem arteries"; when it local- 

 izes in the intima, calcareous plates appear in the vessel 

 walls. Fibroid changes cause the vessels to lose their 

 elasticity, increase the blood pressure, throw an addi- 

 tional strain upon the heart, and further damage some of 

 the viscera, especially the kidneys. If the changes are 

 internal and obstructive, they eventuate in atrophy of 

 the tissue to which the particular vessel distributes. 

 Calcareous vessels become brittle and liable to fracture 

 with resulting hemorrhage. Apoplexy, that so fre- 

 quently carries off the aged, commonly results from 

 the rupture of such vessels in the brain and the destruc- 

 tion and compression of the cerebral substance by the 

 escaping blood. When the peripheral arteries are the 

 seat of sclerosis and calcification and are consequently 

 obstructed, the limbs are sometimes insufficiently 

 nourished and gangrene of the extremities usually 

 of the toes and feet may supervene. 



The nervous system suffers considerably. There can 

 be no doubt but that all of the organs of special sense 

 are more or less embraced in the general atrophic con- 

 ditions for the acuity of all these senses is usually ob- 

 tunded. The vision becomes more and more dimmed, 

 the hearing is dulled, the senses of taste and smell are 

 enfeebled. But the central nervous system also suffers. 

 The brain not infrequently suffers from more or less 



