Search

The development of a coordinated and effective system of community nursing in home and in hospital, for rich and poor, is one of the most vital social problems today

1. We have confirmed the results of earlier workers particularly of Northrop and De Kruif in regard to the following points: (a) the general tendency of the bacterial cell when suspended in distilled water near the zone of neutrality to move toward the anode of an electrical field; (b) the fact that the migration of bacterial cells in the electrical field is a function of the reaction of the menstruum. The curve obtained by plotting velocity of migration against pH passes through an isoelectric point at about pH 3.0, at greater acidity the direction of migration becomes reversed (toward the cathode) and in still more acid solution (pH = 1.0) again disappears; while at reactions less acid than pH 3.0 the velocity is toward the anode and increases with increasing alkalinity; (c) the fact that neutral salts depress the velocity of migration, calcium salts being much more effective than sodium salts of the same concentration. 2. We further find: (a) that on the extreme alkaline side of the curve of velocity of migration plotted against pH a maximum value is reached at about pH 10 with a fall at about pH 12.0 which in many experiments reaches an isopotential point; (b) that the depressing effect of salts is accompanied by a general shifting of the curve of migration velocity so that a maximum velocity (of course absolutely less than that manifest in the absence of salts) appears at about pH 7.0 and an abolition of velocity at pH 9.0 to 10.0; (c) that an apparent "antagonistic" effect is indicated between CaCl2 and NaCl, the presence of a certain concentration of the latter salt diminishing to a slight but definite degree the depressing effect produced by the former; (d) that heat-killed bacterial cells exhibit essentially the same curve of migration velocity as that of the living cells; (e) that bacterial spores exhibit the same general curve of migration velocity as vegetative cells, although the actual velocity is apparently slightly less. 3. All of the observed phenomena appear to be in accord with the assumption that marked differences in dielectric constants did not appear under the conditions studied and if this assumption be granted the results are in accord with the fundamental postulates of the Donnan equilibrium as applied to the explanation of the origin of potential difference between a bacterial cell and its enveloping menstruum. It is possible but not at all certain that the phenomenon of antagonism may require the introduction of additional assumptions for its explanation. Professor Donnan and other investigators have clearly understood the importance of applying the concept of membrane equilibria in the elucidation of physiological phenomena. Our findings add to the numerous vindications favoring this view and emphasize the importance of further study of membrane equilibria in bacterial suspensions. We have pointed out that certain potential differences between bacteria and their menstrua are apparently associated with some of the phenomena of viability. Viability and potential differences may, however, under certain conditions vary quite independently as evidenced by the fact that normal rates of migration are demonstrable after the cells have been killed by heat. Thus, considerable caution must be exercised in relating the existence of these charges to the metabolism of the cell.

WILLIAM F. WELLS, F.A.P.H.A., C.-E. A. WINSLOW, DR.P.H., F.A.P.H.A., AND ELIZABETH C. ROBERTSON, M.D., PH.D. School of Medicine, University of Pennsylvania, Philadelphia; New Haven, Conn.; and Department of Pediatrics, University of Toronto A[CROORGANISMS ordinarily inIVI vade the atmosphere on dust particles, in droplets, or in the nuclei of instantaneously evaporated droplets, normally differentiated as follows: The differentiation by bacteriologic procedure of each of these three classes of air-borne infection has profoundly changed our concepts of disease transmission. Thus the demonstration, a

Professor Winslow has collected in this paper some very interesting comparative statistics with regard to state health laboratories. The progress of public health laboratories in the United States has indeed been remarkable in the last few years. While we may congratulate ourselves on our advance, it is obvious that in many instances much may yet be done to make laboratory of greater value to the citizens of the state.

n/a

n/a

In continuation of work previously reported, upon the viability of B. communis in salt solutions of various kinds,2 we have studied the effect of transfer from salt solutions to weaker salt solutions, in order to see if phenomena could be detected analogous to those observed by Loeb3 and others in the study of the influence of salt solutions upon the swelling of animal membranes and powdered colloids.B. communis was grown on nutrient agar slants at 37° C. for 16-18 hours. The growth was washed off in pure redistilled water, shaken for five minutes to break up clumps and added in 1 c.c. portions to the electrolyte solutions in which the preliminary treatment was to be accomplished (“primary” solutions), which had been previously warmed to 37° C. The solutions were then shaken for one minute to give a homogeneous suspension, 1 c.c. was withdrawn and agar plates poured. The bottles containing the suspensions were then replaced in the incubator at 37° C. and kept there for 30 minutes (in one case 60 minutes)....

1. It seems first of all clear from our results that the effect of electrolytes upon electrophoretic charge is essentially the same, whether one is dealing with silica dust, bacteria, or yeast cells, although certain quantitative differences appear which will later be discussed. 2. The normal negative charge on the suspended particles appears to be slightly increased by very low concentrations of electrolytes, markedly so in the case of yeast cells. Increase in charge due to minimal concentrations of electrolytes has been recorded by Loeb (1922) for collodion particles. 3. Higher concentrations of electrolytes cause a marked and progressive decrease in negative charge, sometimes leading to an isopotential condition and sometimes to a complete reversal of charge with active migration toward the cathode. This effect is apparently due to the cation alone and increases with the valency of the cation, except that the H ion shows specially marked activity, between that of bivalent and trivalent ions. Since NaOH behaves like an ordinary univalent salt, increased alkalinity of a solution does not further depress the charge already depressed by salts; but, since the H ion is much more active than other univalent or bivalent ions, increased acidity does cause a further progressive depression of charge, even in salt solutions. Certain electrolytes appear to show individual peculiarities due to something else than their valency. Thus KCl for example is distinctly more effective than NaCl. Sodium chloride in general appears to exert less influence upon electrophoretic charge, either in low or high dilution, than do other compounds of univalent ions studied. This depressing effect of moderately high concentrations of electrolytes is much less marked with yeast cells than with Bacterium coli. Silica dust is still less affected by monovalent and bivalent ions than are the yeast cells but appears to be more affected than either yeast or Bacterium coli by AlCl3. 4. Very high concentrations of AlCl3 (above 10–2 M) show a third effect, a decrease of the positive charge produced by concentrations of moderate molar strength. This is analogous to phenomena observed for trivalent salts by Northrop and De Kruif (1921–22) and for acid by Winslow, Falk, and Caulfield (1923–24). 5. Organic substances, such as glucose, glycerol, and saponin produce no effect on electrophoretic velocity until they reach a concentration at which viscosity changes are involved. 6. The first two results observed,—(a) the increase in charge as a result of slight additions of electrolytes, and (b) the marked decrease in charge with further concentration of electrolytes, depending on the valency of the cation, so far as vegetable cells are concerned, are entirely in accord with the theory of the Donnan equilibrium as worked out by Loeb (1922). We might assume in explaining such phenomena that the plant cell contains a certain proportion of unbound protein material and that the first modicum of cation which enters the cell is bound by the protein, leading to an increase in the relative negative charge of the cell as compared with its menstruum, while subsequent increments of cation remain unbound in the cell and thus lower its charge. When we find, however, that the same phenomena are apparent with collodion particles, as shown by Loeb, and with silica dust, it seems difficult to apply such a theory, involving the conceptions of a permeable membrane and unbound organic compounds. Loeb (1923–24) suggests that the primary increase may be due to an aggregation of anions in the part of the electrical double layer adjacent to the suspended particles; but why there should be first an aggregation of anions and later (with increasing concentration) an aggregation of cations, is not easy to conceive. The third result,—the reversion to a more negative charge in the presence of a marked excess of trivalent ions,—is again difficult to explain. Loeb, in this connection, postulates the existence of complex ion-protein compounds, which can scarcely be assumed in the case of the silica particles.

n/a