SOME EARLY MICROSCOPISTS 



deposit upon them. This deposit was found to 

 contain minute rods, some of which showed either 

 a steady or gyratory movement. Others were very 

 minute, of rounded form, and moved with remark- 

 able 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 accustomed to drink 

 hot coffee every morning. This, he thought might 

 have killed the animalcules, and his conclusion was 

 confirmed by finding that on the back teeth, which 

 were less exposed to the hot drink, plenty of them 

 were still to be found. In 1697 he tells how he 

 pulled out a decayed tooth, and found that the 

 cavity abounded in moving particles." Nearly a 

 hundred years elapsed before anyone else took up 

 the study of bacteria. 



From the time of Leeuwenhoek onwards, scientific 

 discoveries were announced in rapid succession, so 

 that in one short chapter it is impossible to keep 

 pace with the progress that was made. Among the 

 great men who owe much of their success to the 

 [^X J^icroscope we may mention the Frenchman Reau- 



38 



