374 



SCIENCE. 



[N. S. Vol. XV. No. 375. 



card is isolated by a small card with a win- 

 dow cut in it. The tube and card are 

 viewed in strong diiJuse daylight. The 

 Milton Bradley color scheme has not, how- 

 ever, proved satisfactory for measuring the 

 reduction of nitrates. A large majority of 

 the tubes tested lay somewhere between the 

 reds and the violet reds of the scale, and 

 could not be well matched with either. 

 Some other standards were therefore 

 sought and more suitable ones found in the 

 book of standard colors published by Ijouis 

 Prang, Boston, Mass. This system has no 

 definite scientific basis. The hues are less 

 pure and the tints less bright and clear 

 than in the Bradley system ; the gradations, 

 however, are more numerous. Of the seven 

 plates in the Prang book the last five, in- 

 cluding the darker shades, are not needed. 

 On the ' pure color ' plate and the ' first 

 shade ' plate the colors produced by both 

 the indol and the nitrate test can be quick- 

 ly and easily matched. As far as this 

 standard has been used it has been found 

 to be a satisfactory system of record and 

 an important aid in forming definite ideas 

 as to the behavior of microorganisms un- 

 der various conditions. 



Observations upon the Morphological Va- 

 riation of Certain Pathogenic Bacteria: 

 A. P. Ohlmacher, M.D., Northwestern 

 University Medical School, Chicago, 111. 

 Three observations are here recorded. 

 The first was upon experimentally-induced 

 morphological variation in B. diphtheriw. 

 Here a race, presenting the long, granular 

 or barred type, was transformed to the 

 short, solid type by a forty-eight-hour so- 

 journ in the subcutaneous tissue of a white 

 rat. Two originally short, solid organisms 

 were converted into long, granular ones by 

 a single passage through the organs of a 

 guinea-pig. In the second observation a 

 race of Streptococcus pyogenes from a ease 

 of follicular tonsillitis was observed to as- 



sume the form of a large polymorphous 

 bacillus each of the seven times it was 

 transferred to Loeffler's medium, each time 

 resuming the morphology of the ordinary 

 S. pyogenes longiis Avhen grown in bouil- 

 lon. A race of B. coli communis recovered 

 from a case of gangrenous cholecystitis 

 and cholangitis is concerned in the third 

 observation, in which the organism showed 

 a remarkable polymorphism in the original 

 smears and early generations of cultures, 

 taking on a diversity of forms from long, 

 quite coarse filaments to excessively mi- 

 nute coccoid or diplococcoid organisms. 



Special Laboratory Apparatus: Wm. R. 



CoPELAND, Spring Garden AVater Works, 



Philadelphia, Pa. 



The bacteriological laboratory at the 

 Testing Station of the Bureau for Improve- 

 ment, Extension and Filtration of the 

 Water Supply in Philadelphia, has been 

 equipped with the special object of making 

 examinations of water. Therefore a ther- 

 mostat was designed and built under spe- 

 cial directions. The interior chamber is 

 divided by perforated partitions into four 

 sections. The glass doors, which hang di- 

 rectly in front of these sections, are divided 

 in such a way that the door in front of one 

 section may be opened without exposing 

 the interior of the other sections to the tem- 

 perature of the laboratory. Between the 

 walls of the interior chamber and the sur- 

 rounding jacket, strips of copper are sol- 

 dered, so that water pumped into -the open 

 space between the walls must circulate 

 round all four sides of the interior, before 

 it can escape through the drain. 



The apparatus employed at the Testing 

 Station for filling test-tubes consists of a 

 copper funnel screwed on to a brass pipe, 

 which, in turn, is screwed on to the top 

 of a brass cylinder. Inside of the cylinder 

 is a brass plug containing two holes, one 

 holding ten, and the other five, cubic centi- 



