118 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



is a slight pathological change in the muscle of the 

 heart which marks the beginning of graver altera- 

 tions; in another, the arteries show alterations 

 pointing to a special liability to ruptures or obstruc- 

 tions ; in still another, the blood begins to exhibit an 

 impoverishment which foreshadows progressive losses 

 destined to end in a fatal outcome ; or, again, it is 

 the kidneys, the organs of blood purification, that 

 show signs of being unable to do their duty. These 

 various initial steps in the process of physical 

 degradation may be compatible with what we call 

 good health. The weak places may be revealed 

 only during some period of stress as, for example, 

 during an acute infection. Then the feeble heart or 

 high pressure in the arteries, or the striking pallor, 

 or the refusal of the kidney to obey the calls on it, 

 attracts attention to the presence of structural defects 

 that cast their shadow into the future. The damage 

 thus caused by acute infections in the course of slow 

 processes of a degenerative or involutional character 

 the damage which thus draws attention to the 

 weak parts of the machine must be, in one sense, 

 looked on in the light of an accident. For these 

 circumstances which allow the entry of the tubercle 

 bacillus, or the pus-making streptococcus, by some 

 infective portal, are quite as subject to the element 

 of accident as are the events leading to the fracture 

 of a rib or the severance of an artery. 



Having passed through middle life without con- 

 tracting disease sufficiently grave to obviously im- 



