10 MANUAL OF BACTERIOLOGY. 



the fact that the period of detention was about forty days 

 (Ital. quarantina).* 



Leeuwenhoek, a citizen of Delft, in Holland (1632-1723) 

 appears to have been the first who actually saw bacteria. 

 Yeast-cells he certainly observed, besides making many other 

 contributions of great value to biology. Leeuwenhoek pro- 

 duced admirable lenses of high magnifying power, and de- 

 scribed what he witnessed with singular accuracy and en- 

 thusiasm. 



Even before this time men had sought to explain the phenom- 

 ena of infectious diseases by supposing the body to have been 

 penetrated by minute parasites for example, worms. The 

 spread of such diseases through a community from a single 

 center could readily be accounted for by the multiplication of 

 a contagious element, itself alive (contagium vivum). With in- 

 creasing knowledge of the abundance of microscopic life these 

 speculations took firmer hold. But long before their truth was 

 finally demonstrated great advances were made in the preven- 

 tion of infectious diseases. Much honor is due the clinicians, 

 whose accurate observations and foresight accomplished im- 

 portant results at an early day, working with what now seems a 

 very meagre knowledge of the facts. 



The production of immunity from small-pox by inoculation 

 was first practiced in oriental countries. The method had long 

 been in use in the East, when in 1718 it was brought to the 

 notice of Europeans by Lady Montagu, wife of the English 

 ambassador at Constantinople. The procedure consisted 

 simply of the introduction of the virus of small-pox by puncture 

 of the skin. An attack of small-pox resulted, which was 

 usually much milder and far less dangerous than the natural 

 disease. 



Lady Montagu stated in a letter: "Every year thousands 



*J. M.' Eager. The Early History of Quarantine. Yellow Fever Institute 

 Bulletin, No. 12. U. S. Marine Hospital Service. 



