MICROSCOPIC VS. PLATE COUNT 407 
but even under these conditions there is no good reason why the number 
of bacteria should reach 1,000,000; and it may mostly be brought down 
to below 200,000. In such cities, therefore, milk with more than 1,000,- 
000 bacteria must be regarded as improperly guarded either at the dairy 
or on its transit. 
4+. “ For a Grade A milk higher demands should be made than for 
the ordinary grade. The standard set by the Milk Commission for 
Grade A, viz.; of 200,000 for milk to be subsequently pasteurized or 
for 100,000 to be used raw, is stated by that Commission to be an 
extreme limit for the most unfavorable conditions. Cities situated 
near the supplying dairies should demand a much higher standard, 
which should not allow over 10,000 in bacterial content in Grade A milk 
in communities favorably situated. 
5. “ For communities situated where ice is not available it may be 
necessary to accept a milk with a higher bacterial content; but as 
rapidly as possible the standard should be made to approach the limits 
as given above.” 
Relation of the Microscopic to the Plate Count. The relation of 
Breed’s microscopic to the standard plate count has received some study. 
Brew (1914), after a rather extensive study of the question pointed out 
some interesting facts in his summary. He stated that “ the relative 
differences between the two counts are greater where the bacteria are 
few in number.” In such a case, there is probably an error in the 
microscopic count since it is difficult to see how it is well adapted to 
milks with few bacteria. Brew finds a greater difference when the indi- 
vidual bacteria on the smear are counted than when only groups of 
bacteria are counted. This is said to be due to the fact that a colony on 
a standard plate has developed either from a single bacterium or a 
group of bacteria. Goodrich (1914) reported a marked correlation 
between the two counts. He thinks that, for accurate work, more than 
one slide should be prepared. Brew again studied this relation with the 
aid of Dotterer (1917) and found that the plate counts were higher than 
the microscopic counts on milks with a small number of bacteria. Brew 
has made an attempt to explain this by “ unrecognized contamination ”’ 
on the standard agar plate which would increase this count and by over- 
looking bacteria under the microscope. This seems a rather feeble 
attempt to bolster up the Breed microscopic count in one of its apparent 
deficiencies. More reasonable does it seem that ‘“‘ bacteria where they 
are very few in number, even though well stained and conspicuous may 
not occur in the microscopic fields examined.’”’ This is probably one 
of the major objections to Breed’s microscopic method. Unlike Allen’s 
