476 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



colonies were irregular in outline at the end of about three days, yellowish brown color more- 

 marked iu the center and gradually lading from this point toward the top of the colony. The 

 surface presented a complex network of coarse and tine gi'ooves and markings. The colonies 

 varied in size, being from 2 mm. to 5 mm. in diameter, and to the naked eye had the white 

 mother-of-pearl appearance. There was no liquefaction of the gelatin. In the stick cultures 

 the growth extended along the line of inoculation, had a granular appearance, and grew on the 

 surface of the gelatin around the point of inoculation in the irregular leafy manner like the 

 superficial colonies just described. The movement of the bacilli in the hanging drop were not 

 distinct, and in only one of the three organisms of this group could it be said that there was 

 Ijositive motility. It was demonstrated, however, that all possessed tiagella. Flagella were also 

 shown to be on the colon bacillus used as the standard (in small numbers), although its motility 

 appears doubtful. 



(iiotq) II comprises those organisms obtained from two specimens, and which differed from 

 the colon bacillus in having a rather more prolific growth on agar-agar and gelatin. 



Groiq) III. — The bacilli placed in this group dift'ered from the bacillus of Eschei-ich in the 

 appearance of the colonies in gelatin. They had the appearance of several pale yellow disks 

 superimposed iu an irregular, rosette like manner upon each other, giving one the idea that there 

 were several colonies together. At the end of a week there were a number of smaller colonies 

 joined to the original one by a series of these pale-yellow disks. These bacteria were found iu 

 four of the samples. 



Groiq) IV. — All of the bacteria that could not possibly be mistaken for the colon bacillus 

 were placed here. One of the organisms grew invisibly on potato, and in this resjjcct resembled 

 the typhoid bacillus, but was easily ditlerentiated from that germ by its action with other media. 

 Of the thirty organisms examined, twenty-five produced gas iu the fermentation tube. The tubes 

 used were supplied by Eimer & Amend, of New York, and had the ui)right limb divided off' into 

 five e(iual parts, numbered from abo\e downward. The readings of the amount of gas were 

 made daily, the tubes remaining in the thermostat. The maximum amount of gas was observed 

 at about the third day. It diminished a little by the fourth or fifth day. This gas was treated 

 with a solution of caustic potash to absorb the carbon dioxide; the amount of residual gas was 

 then noted and ignited in the presence of air. There was always an explosion, showing it to be,, 

 probably, composed chiefly of hydrogen. 



The composition of the medium used in the tubes was — 



Chloride of .sodium grains-- 5 



Peptone do 10 



Liebig's meat extract do 3 



Glucose do 20 



Water liter.. 1 



Caustic soda sufficient to make distinctly alkaline. 



The subjoined table gives the readings for the ditterent days for the colon bacillus and the 

 first three groups of organisms: 



