QUANTITATIVE BACTERIOLOGICAL EXAMINATION. 25 



for removing the stopper when that depth is reached. The 

 student will find one good form of apparatus described 

 in Abbott's " Principles of Bacteriology" (Abbott, 1899); 

 an admirable one was devised by Hill and Ellms (Hill 

 and Ellms, 1898). Miquel and Cambier (Miquel and 

 Cambier, 1902) and other authors recommend the use of 

 a sealed glass bulb with a capillary tube which can be 

 broken off at any desired moment. 



As soon as a sample of water is collected its conditions 

 of equilibrium are upset and a change in the bacterial 

 content begins. Even in the purest spring-waters which 

 contain but few bacteria when collected, and in which the 

 amount of organic matter is infinitesimal, enormous num- 

 bers will be found after storage under laboratory con- 

 ditions for a few days or even a few hours. In some cases 

 the rise in numbers is gradual, in others very rapid. The 

 Frariklands (Frankland, 1894). record the case of a deep- 

 well water in which the bacteria increased from 7 to 

 495,000 in three days. Miquel (Miquel, 1891), from his 

 researches, arrived at the conclusion that in surface-waters 

 the rise is less rapid than in waters from deep wells or 

 springs, and that in the latter case the decrease, after 

 reaching a maximum, is likewise rapid and steady. Just 

 how far protection from light, increase in temperature, 

 and a destruction of higher micro-organisms is responsible 

 for the increase, and to what extent an exhaustion of food- 

 supply or the formation of toxic waste products causes 

 the succeeding decrease, we are not aware; but the facts 

 are well established. 



