MICHIGAN ACADEMY OF SCIENCE. 
Ill 
MICHIGAN WATER SUPPLIES. 
VICTOR C. VAUGHAN. 
Mr. Chairman and Gentlemen : The Hygienic Laboratory of the 
University of Michigan was opened in October, 1888. The establishment 
of this laboratory resulted from the activity of the Michigan State 
Board of Health. This Board memoralized the Board of Regents, asking 
that the Legislature be requested to make an appropriation for a State 
Laboratory of Hygiene to be placed under the control of the Board of 
Regents and to become a part of the University of Michigan. The 
memorial stated the objects of the laboratory to be as follows : 
(1) Original investigations into the causation of disease.. 
(2) The examination of food and drink for the health officers of the 
State. 
(3) The instruction of students in hygiene and bacteriology. 
As director of this laboratory since its foundation I have always held 
in mind the above stated objects and have endeavored to direct the 
work of the laboratory along these lines. 
The health officers and other village and city authorities have availed 
themselves of the facilities of the laboratory in the examination of drink¬ 
ing waters used by their communities and up to the present time more 
than one thousand samples of water have been received from officials 
and examined. Some of these have come from other states and will 
not be included in the tabular statements given in this paper. 
The method of examination differs from that practiced elsewhere and 
needs to be briefly stated here. The waters are received in sterilized 
receptacles and immediately on receipt the examination is begun. 
The number of bacteria per cubic centimeter is determined by plate 
cultures. Two sets of plates are made, both of agar; one is grown at 
ordinary room temperature and the other at 37° C. in the incubator. 
Early in our work we discovered that many of the ordinary water 
bacteria do not develop at the temperature of the human body (37° C.), 
while all bacteria pathogenic to man grow best at this temperature. 
Therefore an abundant growth on the plates kept at room temperature 
and a slight growth on the plates kept at 37° C. indicates the presence 
of many saprophytic organisms and the presence of but few, if any, that 
are pathogenic. At room temperature the saprophytic crowd out the 
pathogenic organisms, while at the higher temperature the reverse is 
true. It will be seen that this test is in and of itself of great value in 
arriving at a correct estimate of the danger that lies in the water. 
In the second place beef tea tubes are inoculated with the water and 
these tubes are kept in an incubator, the temperature of which is kept 
constantly at from 38° to 40° C. Usually six tubes are so inoculated, 
the amounts of water in these inoculations running from 0.05 to 1.00 
c. c. These tubes are kept in the incubator for twelve hours, at the ex¬ 
piration of which time, 2 c.c. is injected intraabdominally into rats or 
guinea pigs. If the tubes contain a pathogenic germ the animal is dead 
in twelve hours. As soon as the animal dies it is opened a.septically and 
