FILTH AS infants' FOOD 105 



They multiply in a manner which makes the Mal- 

 thusian formula of geometrical increase look ridicu- 

 lously like failure to maintain the population. We 

 are all more or less familiar with those interesting 

 speculations which at one time played such an im- 

 portant part in the discussion of the so-called Mal- 

 thusian law of population, concerning the number of 

 descendants of a pair of pigeons or a pair of guinea 

 pigs which would exist in the course of a given number 

 of years if nothing interfered to check the increase ; 

 but I venture to say that the progeny of the most 

 prolific animals ever used as terrifying Malthusian 

 arguments would not, in fifty years, equal the num- 

 ber of bacteria produced in milk by a single bacterium 

 in as many hours. If there was nothing to interfere, 

 a single bacterium would produce, in twenty-four 

 hours, seventeen million others P^ While this prolific 

 rate of increase is probably never actually maintained, 

 the normal increase of bacterial population in milk 

 having a high temperature is so astounding- that it 

 defies the mathematical intelligence of an ordinary 

 mind. A cubic centimeter, or about fifteen drops, 

 as much as a quarter of a teaspoonful, will often 

 contain many millions of bacteria. 



It will be understood from this that when the milk 

 in which we are interested at this moment reaches 

 New York its bacterial content is very high. If we 

 could take a sample as soon as it reaches the city, 



