302 The Outline of Science 



veals the life-history. In the course of a few years a very serious 

 bee-pest, known as Isle of Wight disease, has spread throughout 

 Britain, causing havoc among the hives, and greatly discouraging 

 a lucrative and wholesome industry. The nature and meaning of 

 this disease remained baffling until strenuous and patient micro- 

 scopic work by Rennie and White demonstrated that the plague 

 was bound up with the presence of an extremely minute mite in 

 the anterior breathing-tubes of the bee. And when the cause of 

 a disease is discovered, it is not usually long before investigation 

 also reveals a cure. 



Intricacy of Architecture in Small Animals 



Long before there was any microscope the use of the scalpel, 

 helped sometimes by the simple lens, had revealed the intricacies 

 of the body in man and in animals. We may save ourselves from 

 exaggerating modern achievements by recalling how much 

 Aristotle (384-322 B.C.) knew of animal structure. He dissected 

 many a creature, such as the sea-urchin ; he saw the beating of the 

 tiny heart of the unhatched chick; he described how the embryo 

 of the smooth dogfish is bound to the wall of its mother's oviduct, 

 and much more besides. And Aristotle had his successors, few 

 and far between, who kept up the anatomising tradition, long be- 

 fore there was any microscope. But what the early microscopists 

 did was to reveal the fact that the multitude of minute creatures 

 which it was hopeless to try to dissect had an intricacy of structure 

 comparable to that in larger and higher animals. One of the 

 pioneers in this exploration was the Italian, Marcello Malpighi 

 (1628-1694), who described the internal architecture of the silk- 

 worm as animal had never been described before. He worked so 

 hard that he threw himself into a fever and set up inflammation in 

 his eyes. "Nevertheless, in performing these researches so many 

 marvels of nature were spread before my eyes that I experienced 

 an internal pleasure that my pen could not describe." He dis- 

 covered, for instance, the delicate branching air-tubes (or 



