220 THE MINUTE AJSTATOMISTS 



substance of a burning candle turns to water, which, may 

 coagulate and ultimately compose the sixfold corpuscles, 

 perhaps combining with soot particles as it descends. 

 The really important discovery made by Leeuwenhoek 

 was that fermenting wort contains rounded bodies which 

 give off bubbles of gas. 



Bacteria ^ 



In 1683 Leeuwenhoek wrote a letter to the Eoyal 

 Society which contains the first mention of bacteria. 

 He had been writing and speculating upon saliva, and 

 had searched the saliva of the human mouth for animal- 

 cules without finding any. It then occurred to him to 

 ask whether the teeth might lodge animalcules dis- 

 charged from the salivary ducts. He tells us that, 

 though his own teeth were scrupulously clean and par- 

 ticularly sound for his age (about fifty), the lens revealed 

 a white deposit upon them. This deposit was found to 

 contain minute rods, some of which showed either a 

 steady or a gyratory movement. Others were very 

 minute, of rounded form, and moved with remarkable 

 velocity. The largest of all, which were either straight 

 or bent, were motionless. The teeth of an old man, which 

 were never cleansed, contained among others large rods 

 which exhibited snake-like undulations. Rubbing the 

 teeth with strong vinegar did not kill the moving bodies, 

 but they became quiescent when detached and placed in 

 a mixture of vinegar and saliva, or vinegar and water. 

 Nine years later Leeuwenhoek returned to the subject. 

 Living particles were no longer met with in his teeth, 

 and he was at a loss to explain why, until it occurred to 

 him that he was now accustomed to drink hot coffee 



^Phil. Trans., No. 159 (1684), also Arc. Nat. (1683) ; Epist. 75, Arc. Nat. 

 (1692) ; Epist. 110, Ep. Soc. E. (1697). Vol. II, pp. 39-43, 307-311, Vol. Ill, 35-6. 



