The Direct or Breed Method for Counting Bacteria in Tomato Catsup, Pulp or Paste.

The method used for counting bacteria in tomato catsups, pulp or paste depends on the use of the Zeiss blood counter. In this method a drop of catsup diluted with two portions of distilled water is placed in the counting chamber so as to cover the space within the moat. This stands for fifteen minutes before counting.and the bacteria in 25 small squares are then counted and an average is obtained for 5 of these small squares. The result is then multiplied by 2,400,000 to find the number of bacteria per cubic centimeter. This method is described by B. J. Howard (1911) in detail. In counting the number of bacteria per cubic centimeter in a number of samples of catsup I found that this method was not entirely satisfactory, as the bacilli are hard to differentiate from micrococci or various small particles found in the catsup. Micrococci a,re not counted according to this method as they are so liable to be confused with other bodies such as particles of clay. It was thought that these sources of error might be overcome by the use of the direct method of counting bacteria devised by Prescott and Breed (1911), and the same technique was used as that described under the "Microscopic Method of Analysis" in Standard Methods of Bacteriological Analysis of Milk. (A. P. H. A., 1916). The catsup is diluted with two parts of sterile water, since this dilution has proven satisfactory in counting most specimens when the Zeiss counting chamber is used. With a sterile pipette calibrated to deliver 0.01 cc. the diluted catsup is deposited on a second glass slide and evenly spread over an area of 1 sq. cm. by means of a sterile needle. After drying, the