44 DR. K. ANGUS SMITH ON THE EXAMINATION 



alluded to. Perhaps^ however, nitrates prevent decay- 

 in water as. in meat. As the germs of the lower forms 

 of life may pass by us unobserved, it is necessary that we 

 should give them time for development, in order that they 

 may become sufficiently prominent to attract our atten- 

 tion. For this reason I consider it an imperfect exa- 

 mination of water when this is not attended to, in cases at 

 least where we have not the slightest idea of the nature 

 of the water. We find water with less than two grains of 

 organic matter per gallon giving rise to forms by no means 

 agreeable to look at in our food, and water with several 

 grains of organic matter giving rise to no such forms. 



It is true that we cannot tell which of these living forms 

 are most dangerous ; we cannot tell which of them, if 

 any of them, produce either cholera or any other disease ; 

 but we can say that water which contains them may con- 

 tain the elements of disease, whilst water which does 

 not contain them is innocent. So far as this we are 

 obliged to go at present. It was for these reasons that I 

 have not recommended the method of estimating the total 

 nitrogen in water. I was inclined to believe that the 

 danger arising from water could not be measured by the 

 amount of organic matter, or even by the amount of 

 nitrogen in the organic matter. 



Still it is of advantage to estimate the nitrogen of the 

 organic matter, in order to compare the state of one source 

 of water from day to day, as, for example. Dr. Frankland 

 does so frequently in the case of the Thames. It is not, 

 however, the organic matter only that gives out nitrogen ; 

 that is given out by ammonia and nitric acid; and these 

 must also be estimated when seeking albumenoids. And 

 this course is adopted by Profs. Frankland and Wanklyn. 



We may now inquire how far all these bodies together 

 will give us the amount of the organic matter falling into 

 the ^vater. 



