ABSTRACTS 91 



The organisms growing anaerobically may then be drawn off and 

 sub-cultured further in these tubes until practically nothing but anaero- 

 bic organisms will be present. These may be isolated by the anaerobic 

 plate method. 



If successive sub-cultures are to be made from the same tube it is 

 necessary to have the rubber tubing on the burette several centimeters 

 in length so that a pinchcock may be placed about 3 cm. above the 

 original one, the rubber tubing cut with sterile scissors and a sterile 

 burette tip inserted. This is necessary as after one withdrawal of 

 hquid, aerobic organisms may grow in the liquid remaining in the tip. 



Modification in Staining Technic. Zae Northrup. 



The following modification in the technic of Gram's stain is recom- 

 mended for beginning students in bacteriological laboratory work. 

 If a coverglass preparation of two morphologically different organisms, 

 one gram positive, the other gram negative, is made on the same cover- 

 glass and stained by Gram's method, the student is enabled to get the 

 differentiation very clearly. B. coli and B. subtilis lend themselves 

 to this differentiation very nicely. 



Amniotic Fluid as a Bacterial Culture Medium. AVard Giltner and 



L. C. LUDLUM. 



Amniotic fluid is a normal transudate from the blood of the pregnant 

 mammalian female. It is a very dilute albuminous solution contain- 

 ing various salts and also cellular elements in suspension. While its 

 composition varies with the different species of animals and with the 

 stage of pregnancy it was believed that its composition was sufficiently 

 constant and quite probably, qualitatively and quantitatively, in 

 conformity with the food requirements of many parasitic bacteria. 

 In fact it was believed that on account of the ease of collection and the 

 large quantities available, bovine amniotic fluid would serve as a sub- 

 stitute for, or perhaps have advantages over ascitic fluid or blood serum 

 media. At all events amniotic fluid need not be collected aseptically 

 since it can be steriHzed either in the autoclave or by Tyndall's method. 



In our experiments amniotic fluid has been used in place of broth 

 with no additions, and with agar and gelatin or with glycerine. 

 With the colon-typhoid group, B. coli gave excellent growths, B. 

 typhi grew scantily and B. cholerae-suis only fairly well. Staph, 

 aureus grew best on glucose agar and on glycerine amniotic agar. None 

 of the strains of Streptococcus pyogenes studied grew well except in 

 bouillon. The growth was least on the solid amniotic agar which is 

 a fact of considerable interest since, in the few tests conducted, B. 

 diphtheriae from swabs could be isolated readily on the amniotic agar. 

 The isolation of new strains of B. diphtheriae on amniotic agar was 

 facilitated by the inhibiting action on streptococci. Involution forms 

 of B. diphtheriae were not so abundant on amniotic agar as on Loeffler's 

 blood serum medium. An old culture of B. tuberculosis grew with 



