MICROSCOPICAL STUDIES ON TOMATO PRODUCTS. 23 
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 theefigure 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 squares 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. Theruledarea 
sede tot SHEGETH CRE HILRE Hat 
is divided into 16la>ge Sac Nicaea ta 
squares and the num- tetepdert ttt AHL TL bb 
: LSP ml mah Mad 
counted in 8 of these, Ti CIeetee ee tee ene eT al 
which is equivalent to Ht tid 7 oaetaee 
ff saheh oh fest psa ese Theatres 
B28 1/10) cram, (Or PEC Net 
1/20emm. If adilu- HOPE 
tion of one part of the ee eee etecee tees 
EDS Tn Ao 
Enisteris Goad VG of EAE Hae HAH 
ol water is used 1/30 . : ee eet : 
1g ENE 0 ET a aH 
1/20 emm, or 1/50 : io ae nie He fee eae 
cmm as representing LS. LY nu B&B 
the actual amount of 
original stock in 
which organisms are 
taal Gane 1 Fic. 5. Diagram of Thoma rulings. One millimeter divided by lines 
courte pee Obtained. into 20 spaces in each direction, each space equaling 1/20mm. To 
Bacterial count. — facilitate counting, every fifth space is subdivided by a line throvgh 
The rectangles, B, B, ‘em? 
etc., each including 5 of the smallest squares, represent the areas, 
used 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., multiphed by 2.4 million, 
equals the number of bacteria percubic centimeter. Incalculating 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- 
