ROUTINE EXAMINATION OF FECES 115 



at first through absorbent cotton and then paper, and neutralization 

 of the filtrate with sodium hydroxide to pH 6.8-7.0. Before further 

 filtering, 0.5 per cent peptone is added and the medium autoclaved for 

 fifteen minutes at fifteen pounds extra pressure. The albuminous 

 material is filtered off through paper, and the clear filtrate employed as 

 such for whey broth or for the preparation of whey agar. To convert 

 into whey agar add 1.2 per cent of standard shredded or powdered agar 

 to the whey broth. 



The agar plates were prepared by the usual dilution process. The 

 first tube of liquefied whey agar was inoculated with a four millimeter 

 platinum loop, a bi-convex loopful of the standardized fecal suspension 

 (see pages 11-12) being employed. For further dilutions, three and 

 five loopfuls of tubes one and two were transferred. The plates were 

 incubated for forty-eight hours at 37° C. under aerobic conditions. 



B. acidophilus colonies were recognized with the aid of the micro- 

 scope, and their relative number as compared with all other colonies 

 determined. The counting was facilitated by the use of an ocular 

 which is marked off in small squares. There are two types of agar 

 colonies of B. acidophilus designated by Horton and Rettger (1914) 

 as X and Y. The former have a decidedly fuzzy appearance and re- 

 semble small agar colonies oi B. tetani; these are indistinguishable from 

 the colonies of B. bulgaricus. (See Plate II.) The Y type is small 

 and round to spindle-shaped and is only partly fringed, at times appear- 

 ing almost perfectly smooth. 



When in some of the experiments there was any doubt as to whether 

 the observed colonies were those of B. acidophilus or B. bulgaricus 

 transfers were made into maltose (1 per cent) broth and the tubes in- 

 cubated at 37° for at least forty-eight hours. B. acidophilus attacks 

 the maltose and causes a decided acidity which is easily recognized by 

 any of the ordinary tests. B. bulgaricus produces no such change. 

 Morphological studies and milk coagulation tests were made also in some 

 instances. 



The study of whey agar plates gave the most valuable information 

 in so far as the relative numbers of viable B. acidophilus are concerned, 

 and in a most satisfactory way showed the changes that were taking 

 place in the flora from the complex to the simple acidophilus phase, and 

 vice versa. The results are given in the tables in terms of percentage. 



VEILLON TUBES 



The Veillon tube as described by Veillon and Zuber (1898) was em- 

 ployed, with the following modification. Instead of one end being 

 permanently sealed, both ends were left open, and the tube was nothing 

 more than a nine-inch section of one centimeter glass tubing. Previous 



