276 Trans. Acad. Sci. of St. Louis. 
It must be clear from the foregoing illustration that unless 
the samples are collected and transported with the greatest 
care, the results obtained may be far from the truth. It is 
usually not possible nor convenient to test samples at the 
place of collection. I have ona few occasions plated samples 
on the field and the same samples again at the labora- 
tory under favorable conditions of transportation, and 
the results on comparison have always been within the 
limits of error or variation. Except under favorable 
conditions, it is better, in routine work, to have all 
samples sent to the laboratory when it is possible to have 
them properly shipped in ice. While the experiments on the 
effects of transportation were carried out independently, the 
results and conclusions are, for the most part, in accord with 
those obtained by other observers (Jordan and Irons, 1899; 
Whipple, 1901). Samples of water that are chilled will often 
show a decided decrease in numbers, while the same quality 
of water collected during cold weather and subjected to 
similar treatment will often show an increase in the number 
of bacteria. It is also true that waters from different 
sources do not behave in the same way regarding conditions 
of temperature. 
Reception of Sample. — The sample upon its reception 
should receive immediate attention and should not be handled 
except by the person who istomake the examination. Careful 
notes should also be made as to the condition in which the 
sample was received. 
Eaamination of Sample.— Aside from observations on the 
physical properties of the water,—odor, color, turbidity, 
sediment, temperature, etc., the bacteriological examination of 
water divides itself into: (a) quantitative determinations, (b) 
qualitative determinations, and (c) special examination. For 
our purpose, it will be best to take up each of these divisions 
separately. 
Quantitative Determinations.— By a quantitative determi- 
nation we mean the estimation of the number of bacteria in 
a given quantity of water, usually expressed by the number 
of bacteria per cubic centimeter. At the time that the in- 
