DECAY AND DEATH. 999 



food may be increased in density, from semifluid to more or less solid 

 nutrient substances. 



Life has been divided into periods, which may be physiologically 

 thus distinguished. From birth to the appearance of the first tooth, 

 the child or infant may be called a suckling ; from thence to the time 

 when the milk-teeth begin to fall out, is the period of childhood ; 

 thence to the period of puberty, is the age of boyhood or girlhood ; 

 from this to the final completion of the stature, is the epoch of youth 

 or maidenhood ; after that, is the period of maturity. Beyond this, 

 comes the decline of life, and afterwards old age. 



Puberty occurs in the male, at the age of from fifteen to eighteen, 

 according to the climate, and the female, from twelve to fifteen. 

 After the full stature has been attained, a certain development still 

 goes on, the skeleton especially strengthening and solidifying itself, 

 even up to the age of 25 in women, and 28 or more in men. At this 

 period, also, the intellectual powers attain perfection, and the balance 

 between assimilation and waste, is fully established. 



DECAY AND DEATH. 



The life of every organized being depends ultimately on the due 

 and persistent performance of the tissue-changes. These are not only 

 constantly wasting and undergoing repair, through the whole organ- 

 ism, by which means the life of the individual is maintained, but they 

 degenerate and decay. Their nutritive energy becomes enfeebled ; 

 they are no longer renewed or repaired ; their further development is 

 arrested ; the organs no longer perform their various functions ; and 

 then natural decline, decay, and finally death ensue. 



Death may affect a tissue, or a part, or an organ only, of the body ; 

 it is accordingly said to be molecular, or partial, as the case may be ; 

 this is illustrated in ulceration, and gangrene or mortification, of the 

 soft tissues, or caries, or necrosis, of bone. General death, called 

 somatic death (?^, the body), affects the entire system. Partial or 

 molecular death is only followed by general or somatic death, when 

 it interferes with the processes of organic life. Somatic death is the 

 result of a permanent arrest of the circulation. Besides this natural 

 mode of death, or death from old age, or climacteric death, there are 

 unnatural, premature, or accidental modes of death, which may occur 

 at any period or moment. The immediate causes of accidental or un- 

 natural somatic death, are syncope, asphyxia, and coma ; these occur 

 from injury or disease. Old age is the cause of natural somatic death. 

 Coma and syncope have been alluded to in the Section on the Ner- 

 vous System, p. 236, 282 ; and asphyxia is described at length under 

 Respiration, p. 850. They may here be again briefly noticed. 



In syncope, death begins at the heart, this organ either losing its 

 irritability and power of contractility, or being affected with a tonic 

 spasm. In the former case, it is found, after death, flabby and flaccid, 

 with its cavities either filled with blood, or empty ; in the latter case, 

 it is firm and contracted, arid almost or entirely empty. Death by 

 syncope may be occasioned by widely different causes. Thus, it may 



