92 IOWA ACADEMY OF SCIENCES. 



being to determine, if possible, the source of the epidemic. 

 It was recognized after an investigation of the hygienic 

 conditions that the water or milk supply must have been 

 the means of transmitting the germ which caused the epi- 

 demic, A thorough investigation of the water supply 

 proved that there was no indication whatever of any con- 

 tamination; and, naturally, attention was given to the 

 milk supply as the probable cause of the disease. 



A chemical examination was made of every well which 

 supplied water to those who furnished the milk sujDply. 

 All of the samples collected were analyzed at once on 

 reaching the laborator3^ The results of the analysis 

 showed that all of the wells furnished good water except 

 one shallow well, which gave the following results: 



Free Ammouia 054 parts per miilion. 



Albuminoid Ammonia 174 



Solids on Evaporation 904. '' " 



Solids at 180O 752. 



Solids on Ignition 440. " • " 



Nitrogen as Nitrites 2 " " •' 



Nitrogen as Nitrates 24. " " " 



Oxygen consumed in 15 minutes.. .16 " " 



Oxygen consumed in 4 hours 96 " " 



Chlorine as Ciilorideg 24. " " " 



When the results of this analysis are examined it will be 

 noticed that the amount of nitrogen as nitrates is 24 times 

 that of the standard of the State Board of health. The 

 large amount of chlorine and solids in addition to the 

 large amount of nitrogen as nitrates shows most conclu- 

 sively that the well was contaminated. 



A second analysis of water from the same well a short 

 time after the first analysis gave the following results: 



Free Ammonia 104 pai ts per million 



Albuminoid Ammonia 086 " " 



Solids on Evaporation 8 74. " " " 



Solids at 180° 714. " . '• 



Solids on Ignition .506. " " " 



Nitrogen as Nitrates 40. " " " 



Nitrogen as Nitrites 16 " " " 



Oxyeen consumed in 15 minutes. .64 " " 



Oxgen consumed in 4 hours 06 " " " 



Chlorine as Chlorides 26. " " " 



