JOHN W. CHURCHMAN 35 



That certain dyes (acid fuchsin) may exhibit the property in a reverse sense has also 

 been established. These facts are perhaps dependent on the presence of spores in 

 certain bacteria. 



Whatever the explanation, it is sufficiently striking that so hardy an organism as 

 B. subtilis is entirely unable to develop in the presence of a minute amount of gentian 

 violet (1-750,000) or that a vigorous and virulent M. aureus, when stained with this 

 dye, may be injected into susceptible experimental animals without any untoward 

 effects to the host; while, on the other hand, a sporeless organism like B. prodigiosus — 

 easily killed by slight amounts of heat — will grow vigorously in the presence of this 

 dye in dilutions of 50,000, or less, and even though deeply stained, when transplanted 

 to agar will grow apparently as well as the untreated controls. That the parallelism 

 between the gram reaction and selective bacteriostasis although striking is not com- 

 plete, has already been brought out. Reasons have also been advanced why the 

 tempting explanation cannot be accepted that the parallehsm depends on the greater 

 ease with which triphenyl-methane dyes penetrate gram positive organisms than 

 gram negative ones. It is quite possible that in these selective reactions some of the 

 dyes may actually stimulate the growth of the organisms which they fail to inhibit. 



VITAL STAINING 



Much of what has thus far been said applies to bacteria which have been killed 

 during the process of fixation. Since it is well known that profound chemical changes 

 may set in rapidly when protoplasm dies and that disturbance of the cell membrane, 

 as shown particularly by the work of Chambers,' may induce immediate alterations 

 in the cell, care must be taken not to assume too hastily that the phenomena observed 

 in stained specimens represent the facts of the living cell. Such an experiment as that 

 of Benians, in which the bacterial membrane is deliberately ruptured before exami- 

 nation, is perhaps open to criticism on the ground that the treatment provides a differ- 

 ent substance for observation from that present in the living cell. Nevertheless, the 

 examination of bacteria stained in vivo has brought out no facts which are at variance 

 with what has been learned from the staining of fixed smears, Ernst,^ Nakanishi,-' 

 Amato,^ and Pappenheim^ have more particularly studied this subject. Methy- 

 lene blue, brilliant kresyl blue, and toluidin blue have been the dyes chiefly em- 

 ployed. 



A special value of the method of vital staining resides in the fact that what is 

 seen may be regarded as characteristic of the living cell and not an artefact, such as 

 might be produced by staining fixed smears. Large spirilla. Vibrio cholerae, B. typho- 

 sus, and B. coli have been chiefly studied, and particular attention has been paid to 

 the vital staining of the spore. There is little doubt that some difference exists be- 

 tween the accessibility of dead and living bacteria to certain chemical agents. Ny- 



' Chambers, R.: General Cytology, p. 237. 1Q24. 



^ Ernst, P.: Ztschr. f. Hyg. u. Infeklionskrankh., 4, 25. 1888. 



^Nakanishi, K.: Mimchen. med. Wchnschr., No. 6. 1900. 



'•Amato, A.: Centralbl. f. Bakkriol., 48, 2,85. 1908. 



s Pappenheim, A.: Monatschr. f. prakt. Dermatol., 37, 429. 1903. 



