The Dawn of Microscopical Discover//. By C. Singer. 321 



scale, a considerable degree of magnification has been adopted* 

 (fig. 35). 



The occasional use, however, by a naturalist of a simple lens of 

 low magnifying power could have but little influence on the ad- 

 vance of knowledge. Not until the classical period with the 

 invention of lenses of very short focus did the simple Microscope 

 become a valuable means of research. In the pioneer period it was 

 rather the discovery that lenses could be combined into Telescope 

 and Microscope that gave the first stimulus to investigation. 

 These compound instruments were invented about the year 1G10, 

 but whereas the telescope was at once industriously and systema- 

 tically employed by workers of commanding power, the Micro- 

 scope was less happy in its advocates, and observations were few 

 scattered and unrelated to each other. f 



In order to give an idea of the course of development of micro- 

 scopic knowledge, we will first make an historical survey of the 

 knowledge of a particular organism, extending rather beyond the 

 limits of our period, and we will return later to a chronological 

 account of the best pioneer work in other fields. The type organism 

 we select is the little Acarus that produces the disease known as 

 " Scabies " or the " Itch." 



The History of the Itch-Mite. 



The Itch-mite or Sarcoptes scabici is just within the limits of 

 unaided vision. The largest specimens sometimes attain to a size 

 of about 450 fj, by 350 /x. These little Acari burrow in the skin, 

 commencing usually in the hands — whence their name, " Hand- 

 worms," — and spreading thence over the body, they cause intense 

 itching and give rise to a characteristic rash. 



The disease is now a comparatively trivial condition, cured 

 with certainty by change of raiment and externally applied sulphur 

 preparations. Before this rational treatment became general, how- 

 ever, the malady was frequently grave and occasionally fatal, and 

 was treated either ineffectually by internal remedies or laboriously 

 and partially by pricking the little burrows and extracting the 

 organisms separately with a needle. This was a process that 

 required patience and faith on the part of the sufferer, and on the 

 part of the operator (usually a woman) the same qualities with the 

 addition of exceptionally good near vision. " How cruel a disease 



* Fabio Colonna. " Minus cognitarum stirpium aliquot ac etiam rariorum 

 nostro coelo orientium e/c^pao-is," Rome, 1606. The description of the lichens 

 figured is on p. 331 of this work. 



t The present writer has given a general review of the early history of the 

 instrument in his "Notes on the Early History of Microscopy," Proceedings of 

 the Royal Society of Med. 1914, vol. vii. (Section of History of Medicine), 

 pp. 247 79. 



