1911.] The Influence of Ionised Air on Bacteria. 237 



It may then be concluded that the bactericidal effects observed in the 

 photographs are not due to the influence of ultra-violet light, bactericidal 

 rays of which would freely penetrate the thickness of air and quartz used. 



In order next to shield the organisms from the direct wind by interposing 

 a stout membrane between the point and the agar, a plate was prepared and 

 sown upon which a cigarette paper was laid moistened with the emulsion. 

 The discharging points were arranged to be on the centre line of the paper, 

 and the exposure was, as before, half an hour. The effect, also given in 

 fig. 21, shows that the negative discharge penetrates the moist paper, though 

 it is not so active as without the paper. This result, that the destructive 

 influence can penetrate a membrane like wet paper in contact with bacteria, 

 is of importance in showing that the electrical charge of ionised air may be 

 expected to pass through lung membranes into the blood. 



There is, however, in the present case a third possibility, that the action is 

 not caused by the ions carried with the electric wind but by some 

 penetrating radiation independent of it. To test this a light wire frame was 

 made to hold a cigarette paper, dry or moistened as before, 3 mm. hori- 

 zontally above the surface of the agar, which had been sown as usual. The 

 result was that there were no cleared areas under the points. The whole 

 effect may therefore be attributed to the direct influence of, and contact 

 with, ions in the electric wind. 



9. It was shown in the previous paper that both red corpuscles and 

 leucocytes have a strong negative charge. On the other hand, fresh bacteria 

 have a charge positive in sign and of the same order mass for mass as that of 

 the blood cells. 



The chief function of leucocytes is known to be that of absorbing bacteria 

 from the blood. Their thin walls are easily pierced, but the origin of the 

 force necessary for this to take place has not been located. The general 

 conception of chemiotaxis, covering all movement in response to chemical 

 stimulus, has been the closest approximation. It is now suggested that the 

 initial stimulus to the process of absorption may be more simply explained 

 by the attraction of the positively charged bacteria by the large negatively 

 charged leucocytes. In the case of fresh blood cells the electrical charges 

 are very fixed and characteristic, as shown by the rapid and uniform 

 movement of the cells in strong electric fields. The charge of bacteria, 

 however, invariably reverses when the culture is kept for several days.* 

 The negative chemiotaxis described by Bordetf would then have to be 



* 'Roy. Soc. Proc.,' B, 1910, vol. 82, p. 641. 



t J. Bordet, "Studies on the Serum of Vaccinated Animals," ' Annales de la Societe 

 Boyale des Sciences medicales et nat. de Bruxelles,' 1895, vol. 4. 



