HEALTH AND DISEASE 355 



destroyed the potato crop in 1 845 and drove many of the Irish people to 

 America, and of the powdery mildew which wiped out the wine industry 

 of Madeira and forced the population of that little island back to their 

 ancient occupations of sugar-cane growing and cochineal gathering. 



The story of the Irish potato blight is the story of a microscopic fungus 

 which wrought havoc in Europe equalled by few of Europe's many wars. 



It is believed that the potato was first brought to Europe by Sir Francis 

 Drake from the Andean hinterland of South America, where it had long 

 been revered, emblematic of fertility, and even been the inspiration of 

 mutilation and human sacrifice. Thanks to the efforts of Sir Walter Raleigh 

 and many other enthusiasts, the potato soon won its rightful place as a lead- 

 ing source of carbohydrate food throughout all of Europe, from the Medi- 

 terranean to northernmost Scandinavia, and in northeastern North Amer- 

 ica as well. In its migration from South America the potato had left 

 behind its most serious agents of disease; for two hundred years or more it 

 enjoyed comparative freedom from disease. But in the early half of the 

 nineteenth century, disturbing reports of potato failures began to appear. 

 In ever-increasing intensity, a plague of potato fields was laying waste the 

 crops of individual farmers, and of whole communities. 



In 1 845 the crisis was reached. With unbelievable fury the potato blight 

 devastated millions of acres in Europe, the United States, and Canada. So 

 sudden was the catastrophe and so complete that in only a few days fields 

 with every promise of abundant harvest were transformed into blackened 

 wastes of vegetation overlying foul and putrifying masses of rotten tubers. 

 And this was not a local problem, nor limited to a few fields, — everywhere 

 where potatoes were grown the tragedy was repeated, bringing in its wake 

 privation, then starvation or the fever that inevitably follows malnutrition. 

 In Ireland alone, a quarter of a million people fell victim to the famine, and 

 many others migrated to America and became the basis of the Irish- 

 American population of the United States. 



Like most tragic experiences of mankind, the potato blight was not with- 

 out some benefit. In the nineteenth century science was rapidly throwing 

 off its stupor of the Middle Ages: the chains of superstition that so long 

 had bound and suppressed creative thought were rusting away. The intel- 

 lectual genuises Louis Pasteur and Robert Koch were performing the first 

 crucial experiments that were to open up the vast field of modern research 

 on contagious disease. Charles Darwin was revolutionizing biology and 

 philosophy with his keen deductions on organic evolution. Von Liebig was 

 laying the foundations of modern agricultural chemistry. The stage was 

 set for the first fundamental discoveries on the nature and control of plant 

 disease, and the catastrophe of the potato blight forced the attention of 

 master minds to the solution of this and related problems in plant pathology. 

 Out of the labor pains of Europe, racked by the potato blight, was born 

 modern plant pathology, the science of plant disease. The brilliant young 



