FEBRUARY 9, 1912] 
Results will appear in a Bulletin of the New 
York Agricultural Experiment Station. 
Suggestion of a New Method of Stating Com- 
posite Results of Bacterial Milk Counts: ERNEST 
C. Lrvy. 
Statement of the ‘‘average bacterial count’’ of 
milk samples in any city is of comparatively little 
value on account of the influence of a few samples, 
or even a single sample, of very high bacterial 
content. 
The most approved method of statement of re- 
sults has therefore been to give the number of 
samples, and the percentage of samples, falling in 
each of certain more or less arbitrary groups or 
classes, in the following manner: 
No. of Per Cent. of 
(A) Class Samples All Classes 
Under 10,000 ....... 25 16.7 
10,001 to 50,000 ....... 73 48.6 
50,001 to 100,000 ....... 37 24.7 
100,001 to 250,000 ....... 9 6.0 
If we apply this method to the hypothetical 150 
samples given under (4) we get the following: 
No. of 
Rating Samples in 
(@) Class Figure Each Class Product 
Under 10,000 ..... 100 25 2,500 
10,001 to 50,000 ..... 90 73 6,570 
50,001 to 100,000 ..... 75 37 2,775 
100,001 to 250,000 ..... 50 9 450 
250,001 to 499,000 ..... 20 3 60 
Over 500,000 ..... 0 3 0 
Mo tals emmy Meine secs eeaeiee 150 125355 
SClahouGinel Inlay SounsnasoanoouconObeoe 82.4 
250,001 to 500,000 ....... 3 2.0 
Over 500,001 ....... 3 2.0 
Oba sevelatsisqeusvereysieeins 150 100.0 
This method, while of more real value than a 
mere statement of average count, is too cumber- 
some. In order to get around these difficulties, a 
new method of statement—the ‘‘bacterial index’’ 
—is suggested. To each of the groups above 
shown a rating value is given, as follows: 
Suggested Rating 
Figure for Raw 
(B) Class Milk 
Winskxe AOC) -conscocooaceo 100 
TOO fi BOM ccescosovadeso 90 
50,001 to 100,000............ Bion) 
100,001 to 250,000 .............. 50 
250,001 to 499,000 .............. 20 
Over 500000 eee ee eeeeee ee 0 
SCIENCE 
233 
The bacterial index thus arrived at takes into 
account the number of samples falling in each 
class, but at the same time enables us to state our 
results in a single figure, and this figure is not 
unduly influenced by exceptional samples. The 
method itself is believed to be of real value, but 
the rating figures given are only suggestive and, 
if the method is adopted for general use, proper 
rating figures should be agreed upon after careful 
consideration by some competent body of bac- 
teriologists. 
In applying the method of statement to samples 
of pasteurized milk, a different set of rating 
figures should be used. We know less about this 
than about raw milk, but the following ratings are 
given as illustrative: 
Suggested Rating 
Figure for Pas- 
(D) Class teurized Milk 
(Und er ertlO Omi atvstnemteebs rc: cis tre 100 
TOU Como OOMsarsersparycreeeses eee 90 
UL ABN Gocoostocusosdoce 75 
TOOTS tone: O00 Ole ereee es te epace 50 
SAVOIL to) OOO) svoosseccodsoscacves 20 
Over FO: 000m permet eee eee 0 
An additional advantage of using the bacterial 
index in stating results for pasteurized milk 
samples is that we get around the danger of 
having misleading comparisons made between the 
bacterial counts of raw and pasteurized milk. 
Instead of this, with proper rating figures for 
each kind of milk, we can compare any group of 
taw samples with ideal raw milk and any group of 
pasteurized samples with ideal pasteurized milk. 
The Control of Pasteurized Milk by Physical and 
Bacterial Standards: Winu1aM Royau STOKES 
and FRANK W. HACHTEL. 
The article after emphasizing the importance 
of the control of the pasteurization of milk and 
of milk after it has been pasteurized described 
the bacterial reduction obtained through the pas- 
teurization of milk by means of the so-called 
*“slow’’ and ‘‘rapid’’ methods. It then men- 
tioned the physical and bacteriological standards 
for the control of pasteurization which were es- 
tablished by Koehler and Tonney, of Chicago. 
The minimum temperature requirements for the 
continuous or rapid type of pasteurization are 
160° F. (71° C.) for one minute, and for the slow 
or ‘‘holding’’ method 140° F. (60° C.) for twenty 
minutes. These requirements have been adopted 
