66 PHARMACEUTICAL BACTERIOLOGY. 



Based upon such conditions as can be made to prevail in carefully oper- 

 ated factories, the following may be given as the limits of the number of 

 organisms permissible in the fruit products under discussion. 



a. Yeast cells, either living or dead, not to exceed 1,000,000 per c.c. 



b. Moxild spores not to exceed 50,000 per c.c. 



c. Hyphal clusters and hyphal fragments not to exceed 10,000 per c.c. ; 

 or not over 50 per cent, of separate and distinct fields of view under the 

 compound microscope should show hyphal clusters or hyphal fragments. 



d. Bacteria (either living or dead but not including vinegar bacteria in 

 products to which vinegar is added) not to exceed 5,000,000 per c.c. 



The above figures apply only to fruit products supposedly made from 

 comparatively fresh fruits and fresh fruit juices. The yeast, bacterial and 

 spore counts are made with a Thoma-Zeiss hemacytometer (Turck ruling) 

 using a No. 5 (i/s in.) objective with No. 2 (i in.) ocular. 



H. Quantitative and Qualitative Bacteriological Testing. — The following 

 will serve as a general outline of bacteriological analyses which may be made 

 in food and drug laboratories. The substances which require such bacterio- 

 logical examination include catsups, tomato pastes, vinegars, water supplies, 

 mineral waters, milk, ice creams, any and all substances which are suspected 

 to be sewage contaminated, etc., etc. 



The sequence of processes here given bear a progressive relationship. 

 Whether process II is carried out will depend upon the findings under I and 

 whether III shall be undertaken will depend upon the findings under II. The 

 essential facts to be ascertained are whether or not there is possible sewage 

 contamination as indicated by the presence of the colon bacillus, sewage 

 streptococci and possibly the typhoid bacillus. The typhoid agglutinating 

 tests are apt to prove unsatisfactory. In most instances this test will be 

 unnecessary as the presence of the colon bacillus is evidence that the 

 food, drug or drink is contaminated with sewage and is hence unfit for 

 human use. 



I. Direct Count. — ^For this purpose the Thoma-Zeiss hemacytometer 

 with Turck ruling^ is used (No. 2 ocular with 1/5 in. objective) which can be 

 secured from any bacteriological supply house. The instructions for using 

 it can be obtained from the dealer, though the measuring values indicated 

 on the hemacytometer are suflGicient to indicate the manner of making the 

 counts. The rulings generally used for bacterial countings are 1/25 sq. mm. 

 X i/io mm. deep, making an area of 1/250 cu. mm., or reduced to decimal 

 fractions, 0.04 sq. mm. X o.i mm. deep = 0.004 cu. mm. We will suppose 

 that the average of 20 counts shows 5 bacilli, then i cu. mm. would contain 

 1,250 bacilli or 1,250,000 in i c.c. 



The direct count is, in many instances, very unsatisfactory for several 



' To render the ruled lines visible rub a very soft pencil over the ruled area. 



