660 



SCIENCE 



[N. S. Vol. XLI. No. 1061 



structural difference to separate generieally all 

 Judith Eiver, Belly Eiver and Two Medicine 

 trachodonts from those obtained in the Lance 

 formation, and that therefore the use of the 

 term Trachodon should be restricted in its 

 application to some one of those trachodonts 

 found in the older beds. 



3. That the restriction of the genus Olao- 

 saurus to the Niobrara species 0. agilis Marsh 

 first proposed by Hatcher be endorsed. 



4. That Claosaurus annectens Marsh should 

 be regarded as a synonym of Thespesius occi- 

 dentalis Leidy as first proposed by Lucas. 



Charles W. Gilmore 

 TJ. S. National Museum, 

 January, 1915 



THE SOCIETY OF AMEBICAN BACTEEIOL- 

 OGISTS. II 



Technique 

 Under the supervision of G. F. Ruediger 

 The Bacteriological Work of the Bureau of Chem- 

 istry and Its Possibilities: Charles Thom. 

 The papers presented by members of the bac- 

 teriological staff of the Bureau of Chemistry are 

 fairly representative of the manner in which nu- 

 merous problems arising from the enforcement of 

 the Food and Drugs Act are being met by the bac- 

 teriological laboratory. Very many of the food 

 products and other preparations met with in inspec- 

 tion work have not been adequately studied by bac- 

 teriologists. No analysis of the flora present in 

 such substances is available. Standard methods 

 for testing them have not been developed. The 

 workers into whose hands they fall must then make 

 . a full study of several to many brands of the com- 

 mercial article and very frequently follow the 

 product every step of the way back to the actual 

 producer before adequate data can be obtained to 

 determine what action, if any, shall be taken by 

 the bureau. The members of the Bacteriological 

 Society are earnestly requested to aid this work 

 whenever opportunity arises by studying the bac- 

 teriological conditions obtaining in food-stuffs and 

 the standardization and publication of methods of 

 procedure. 



In addition to its inspection work, the bureau 

 is now establishing a research laboratory to take 

 up food deterioration, fermentation and technic- 

 ally bacteriological and myeological work upon 

 unsolved problems concerning foods and drugs. 

 This work will be carried in the closest possible 



cooperation with the chemical laboratories of the 

 bureau dealing with the same related problems. 

 By these two methods of attack it is hoped to en- 

 large our knowledge of the flora of food stuffs and 

 the relation of these organisms to normal and ab- 

 normal conditions as found. 



Methods of Counting Bacteria: Eobekt S. Breed. 



Three methods of counting the number of bac- 

 teria present in various substances have been gen- 

 erally recognized. In order of their historical de- 

 velopment, they are the microscopical method, the 

 dilution method and the plating method. For the 

 past few years, however, the latter method has 

 been used, especially among American bacteriolo- 

 gists, almost to the exclusion of the others and 

 this, in spite of the fact that what little compara- 

 tive work has been done indicates that certain 

 uncontrollable elements in this technique cause 

 large errors. 



Among other causes of irregularities in the 

 counts, there are two which tend to lower the 

 count in both the dilution and the plating method. 

 One of these is the fact that the organisms pres- 

 ent in the substance under examination may faU 

 to grow in the culture medium used, and the other, 

 tliat the clumping of the organisms reduces the 

 number of centers from which growth occurs. 

 The microscopical technique is free from these 

 objections, but it is open to another in all cases 

 where a count of living organisms only is desired. 

 This objection arises because of the fact that it 

 is ordinarily impossible to distinguish organisms 

 which were alive at the time the preparation was 

 made from those which were dead. This difficulty 

 causes the count obtained in this way to be higher 

 than it should be. 



These conditions which have thus far proved to 

 be uncontrollable in all of the three methods are 

 largely responsible for the big discrepancies in the 

 comparative counts which have been made. These 

 discrepancies show most strikingly that all so- 

 called bacterial counts are much better styled 

 ' ' estimates ' ' than ' ' counts. ' ' Statements that 

 certain substances, such as milk, water, sewage and 

 the like, contain such and such numbers of bac- 

 teria are particularly unfortunate, for they are 

 plain misstatements of facts. In most cases the 

 figures given represent counts of colonies on agar 

 or gelatin and may be properly so recorded but 

 these figures are usually far below the actual num- 

 ber of bacteria present. 



So far as raw milk is concerned, microscopical 

 methods of counting have been shown to have 

 great usefulness, for, in these cases, the number of 



