;i8 THE PHYSIOLOGY OF REPRODUCTION 



SENESCENCE 



As age advances, in addition to the menopause changes which 

 relate more especially to the cessation of the female generative 

 functions, atrophic changes of one sort or another take place in both 

 sexes throughout practically the entire system. The internal spongy 

 structure of the bones is dissolved away, so that they are left with 

 only a hard external shell and consequently become brittle. The 

 teeth decay and drop out. The muscles shrink in volume, the actual 

 fibres of which they are composed becoming smaller in size and fewer 

 in number. The arterial walls lose their elasticity and undergo 

 sclerosis, a characteristic which is so constant that it has given rise 

 to the well-known dictum that " a man is as old as his arteries." 

 The tendons and ligaments also become calcified, and there is a 



FIG. 185. Section through vaginal mucous membrane of woman of 

 sixty-one. (From Sellheim.) 



consequent shrinkage of stature. The size of the liver and other 

 viscera undergoes diminution, but the kidney and heart retain thoir 

 size ; in fact the heart is usually slightly enlarged in old age, but this 

 apparent hypertrophy is not associated with an accession of power 

 but with an increased feebleness, and the pulse, in order to 

 compensate for the weakness of the enlarged heart, beats more 

 quickly, the normal rate of seventy-two beats per minute rising to 

 seventy-nine or eighty. The rate of respiration also rises slightly, 

 and the vital capacity of the lungs diminishes. Moreover, the 

 amount of carbon dioxide and urine which are excreted becomes less. 

 The pigment in the hair undergoes absorption, the hair turning grey 

 or white. The adipose tissue beneath the skin disappears, especially 

 in advanced old age, but fatty degeneration of muscle or glandulaf 

 tissue is not infrequent. In the male sex the prostate gland under- 

 goes atrophy, or in some cases a pathological hypertrophy, which is 

 said to be the cause of frequent penile erections. 



