442 Dr. C. Shearer. On the Toxic Action of Dilute Pure 



This experiment clearly demonstrates the four following points : — 



1. The toxic action of a pure - 85 per cent. NaCl solution on the meningo- 



coccus. 



2. The antagonistic action of a trace of CaCl2 solution over the toxic action 



of the NaCl. 



3. The accelerating action of KC1, when added to CaCl2, in antagonising 



the toxic action of NaCl. 



4. The relatively harmless action of distilled water on the meningococcus. 



So definite is this toxic action of 0'85 per cent. Nad solution on the 

 meningococcus, that it was found possible to make use of it, very successfully, 

 to destroy all meningococci outside or attached to the surface of leucocytes, 

 by simply washing these several times and allowing them to stand for a few 

 hours in a small bulk of pure saline.* 



There is no doubt that in this toxic action of dilute NaCl solution on the 

 meningococcus we are dealing with the poisonous action of the Na cation, so 

 extensively investigated by Loeb,f Wasteneys,t Osterhout,§ and others. 



It is interesting to find that in the case of the meningococcus, as these 

 investigators have found for other forms of life, this toxic action of NaCl is 

 confined to relatively dilute solutions. In the case of the meningococcus, 

 it is essential that the concentration of the NaCl should not be increased 

 much beyond - 9 per cent., as after this point its toxic action rapidly 

 decreases. The use of a 1*5 per cent. NaCl solution (one of the standard 

 strengths of this salt employed in opsonic work) is without almost any toxic 

 action on the meningococcus, as shown by the following experiment : — 



A fairly thick emulsion of a 24 hours' culture of meningococcus " Pry or " 

 was made (about 5000 million cocci to the cubic centimetre). To 4 c.c. of a 

 pure 1*5 per cent. NaCl solution, 25 cu. mm. of this culture, in distilled water, 

 was added, and thoroughly mixed. To 4 c.c. of - 85 per cent. NaCl solution 

 a similar quantity of the same emulsion was added and mixed. The two 

 solutions were placed in the incubator at 37° C. for an hour. They were then 

 taken out and centrifuged, and the deposit planted out separately on the 

 surface of a chocolate plate, as shown in fig. 2. This figure shows the 

 resulting growth obtained on this plate after 24 hours' incubation at 37° C. 



The - 85 per cent. NaCl solution (marked N in the plate) has killed the 

 meningococcus, while a good growth has been obtained on that half of 



* See paper by Shearer and Crowe, " The Role of the Phagocyte in Cerebro-spinal 

 Meningitis," ' Boy. Soc. Proc.,' B, vol. 89, p. 422 (1916). 



t Loeb, ' Collected Papers,' Part II, University of Chicago, 1906. 

 % Loeb and Wasteneys, ' Journ. Bio. Chem.,' vol. 21 (1915). 

 § Osterhout, ' Zeit. f. Physkl. Chem.,' vol. 70 (1910). • 



