MICROSCOPICAL STUDIES ON TOMATO PRODUCTS. Da 
EXPLANATION OF CALCULATIONS. 
Figure 5 has been prepared to make somewhat clearer the expla- 
nation of the areas denoting the yeast and spore and bacterial counts. 
The light lines in the figure show the arrangement of rulings cn the 
entire slide. The squares (A, A, etc.) and rectangles (B, B, etc.) 
designated in theeigure by the heavy lines indicate the portions used 
for the yeast and spore and for the bacterial counts, respectively. 
The 8 large squares, A, A, etc., are the syuares used for yeast and 
spore counts. Each of these squares has 25 of the small squares. 
The sum of the organisms counted in the 8 squares marked A, A, 
etc.,is the number in 1/60 cmm.if a dilution of one part of product 
to two parts of water is used. 
Yeast and spore count.—The ruled square on the slide is 1 mm on 
- each side and the cell 
is1/10mmdeep. The 
volume of the ruled 
part is therefore 1/10 
emm. Theruledarvea 1 
is divided into 16 lazge HAS HA Beane. aan 
squares and the num- HZSS enema eeee! pH ebdabs 
ber of organisms is 7-alp Aan Spitneriinns = 
counted in 8 of these, mt BRESHINEELIEE m3 nee = 
which is equivalent to aE Gun 
1/2 of 1/10 emm, or igaaciagee i ae 
i cmm. If adilu- EE-HIEEAI ae 
tion of one part of the 
product to two parts 
of water is used 1/3 of 
¥/20 ‘emm, or 1/50 : 
emm as representing Aon 
the actual amount of 
original stock in 
which organisms are 
i 
Pan) Gavlobtnined Fic. 5. Diagram of Thoma rulings. One millimeter divided by lines 
counted, 1S Obtained. into 20 spaces in each direction, ea~h space equaling 1/20mm. To 
Bacterial count. — facilitate counting, every fifth space is subdivided by a line throvgh 
The rectangles, B, B, ‘m7 
ete., each melaas 5 of the smallest squares, represent the areas, 
used i in making the bacterial count. Similar rectangles of equal area 
might beselected, the object being to count 5such areas well distributed 
over the ruled portion of the slide. The average number of bacteria 
counted on 5 rectangles, such as B, B, etc., multiplied by 2.4 million, 
equals the number of bacteria percubic centimeter. In calculating the 
bacteria, it is observed that there are 400 (20 x 20) small squares on 
the slide. The number of bacteria in rectangles (B, B, etc.), each 
containing 5 of these small squares, are counted and an average made. 
This average represents the bacteria in 1/80 of the total ruled area. 
Since the cell is 1/10 mm deep, the volume represented by the organ- 
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