BIOLOGY IN HUMAN AFFAIRS 



devising adequate, if cumbersome, methods of control of 

 both typhoid fever and Asiatic cholera. Various poisons, 

 apt to affect large groups — lead, arsenic, ergot — were also 

 detected, and rational means for their control were devised. 

 In nutritional disease nothing important was discovered 

 until about the beginning of this century, with the excep- 

 tion of the significant fact that scurvy could be prevented 

 and cured by feeding fruit juice or fresh vegetables. The 

 mere classification of foods into their caloric content, useful 

 enough in its way, ignored the much more significant con- 

 tent in vitamin, the discovery of which has revolutionized 

 our notions of nutrition. The fact of infestation with 

 certain animal parasites was recognized, but little was done 

 to prevent it. On the social side, health organizations began 

 to be established as it became apparent that something 

 could be done in a governmental or community way to 

 control at least some of the worst of the besetting diseases. 



This very brief and cursory review brings us up to the 

 period of the discovery of bacteria and their important role 

 in the causation of sickness. Far more important for 

 humanity than the demonstration of the bacterial cause of 

 this or that particular disease, was the generalization by 

 Pasteur that germs do not originate spontaneously, but 

 are always the ofi'spring of antecedent organisms of the 

 same kind. It is on this generalization that one important 

 branch of present-day public health work is based. Obvi- 

 ously, if germs could originate spontaneously in filth, 

 water, or soil, their control would be virtually impossible. 

 On the other hand, if they came only from ancestors in 

 kind, these having their common habitats in the bodies of 

 persons sick with particular and recognizable diseases, 

 something might be done to prevent their spread to those 

 who are well. 



Public health work has had different beginnings in 

 various environments. In England, for example, it is said 



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