Septembek 19, 1913] 



SCIENCE 



409 



Further experiments show clearly that false 

 plasmolysis plays a part in this process, for 

 hypotonic solutions or even tap water or dis- 

 tilled water may produce a contraction of the 

 inner surface while the turgidity of the outer 

 surface is maintained. 



The chromatophores are numerous and lie 

 embedded between the inner and outer sur- 

 faces of the protoplasmic sack. They contain 

 <!hlorophyll and likewise a red pigment which 

 is soluble in water. The red pigment is 

 unable to escape from the chromatophore into 

 the protoplasm under normal conditions be- 

 cause the surface of the chromatophore is 

 impermeable to it. When the separation of 

 the inner and outer surfaces of the protoplasm 

 reaches a certain point the surface of the 

 chromatophores usually becomes permeable to 

 the red pigment so that it diffuses out. The 

 cells then present a very striking appearance. 

 The contracted vacuole remains colorless while 

 all the space between the inner and outer sur- 

 faces of the protoplasm becomes deep red. 

 The red pigment can not escape through the 

 outer surface, nor can it pass through the 

 inner surface into the vacuole. The cell may 

 remain in this condition for an hour or two. 

 Finally the red color begins quite suddenly to 

 diffuse through both the protoplasmic sur- 

 faces. 



The nuclei behave as though their surfaces 

 were impermeable to the red pigment at the 

 start, but they appear to become permeable to 

 it soon after it begins to diffuse out from the 

 chromatophores. 



The cell wall which encloses the protoplasm 

 is freely permeable to the red pigment and to 

 salts at all times, but is quite impermeable to 

 many other substances. 



Similar effects have been observed in a 

 variety of other cells. 



Whether these effects are due to true or to 

 false plasmolysis or to a combination of both, 

 it is evident that the various kinds of surfaces 

 (i. e.j the inner and outer protoplasmic sur- 

 faces, and those of the chromatophores, of the 

 nuclei and the cell walls) can be proven to 

 differ greatly in their behavior with respect 

 to permeability. 



The term differential permeability may be 

 suggested as an appropriate designation of 

 these phenomena. 



The conception of differential permeability 

 may perhaps be extended to surfaces other 

 than those described here. Since the proto- 

 plasm is composed of a variety of structures 

 (down to those which are ultramicroscopic) 

 and each of these has a surface it is quite 

 possible that many kinds of semi-permeable 

 surfaces exist within the cell. 



w. j. v. osterhout 

 Haevaed University, 

 Laboeatoet op Plant Physiology 



THE SOCIETY OF AMERICAN 

 BACTEBIOLOGISTS. II 



sanitaey bacteeiology 

 Observations upon the Bacteriology of the Balti- 

 more City Water in Selation to the Typhoid 

 Fever Present, and the Effect of the Hypochlo- 

 rite Treatment: William W. Ford and Eenest 

 M. Watson. 



Since October, 1910, up to the present time 

 (December, 1912), a period of a little over two 

 years, it has been possible for us to foUow the 

 bacteriological condition of the Baltimore city 

 water by systematic examinations (weekly) — ex- 

 cepting for a brief period in the summer of 1911. 

 These examinations have been of the nature of the 

 bacterial count, the determination of the number 

 of fermenting organisms present by means of the 

 Smith tube, the isolation and determination of the 

 various species present. The purpose of this work 

 was (1) to determine the relation, if any, between 

 the extent of the pollution and the amount of 

 typhoid fever in the city, (2) to determine the 

 seasonal variations in the bacterial content of the 

 water and (3) to ascertain the effect of alum and 

 hypochlorite of lime upon the city drinking water, 

 as regards the bacterial content and later the 

 effect of the purity or pollution of the water under 

 these conditions upon the amount of typhoid fever 

 in the city. It was found that in 1910 and 1911 

 there was a striking relation between the period 

 of summer and fall pollution of the water and the 

 summer rise in the amount of typhoid fever. The 

 number of organisms in the water at this time 

 ranged from 1,000 to 5,000 per cubic centimeter, 

 and fermentation took place in 1/10 to 1/100 c.c. 



