I'Z THE FLOCCULATION OF BACTERIA, 



precipitated tricalcium phosphate are so like large clumps of 

 bacteria that they might readily be mistaken for such. In a 

 mixture of phosphate particles and bacterial clumps, differences 

 are to be seen in the smaller clump's where the individual bacteria 

 can be recognised. That nascent calcium phosphate should 

 flocculate bacteria is to be expected from the fact that, as well as 

 being non-diffusible, it has an affinity for loose water molecules, 

 and forms with them hydrated calcium phosphate. Soon after 

 formation it becomes less and less hydrated, and when added to 

 cultures at this stage no flocculation of bacteria occurs. 



We can now refer to the differing susceptibilit}^ of the three 

 experimental organisms to the action of calcium chloride. Micro- 

 scopical examination of the precipitates did not indicate anything 

 unusual, because the precipitated calcium phosphate looked pre- 

 cisely like large clumps of bacteria. There are two causes that 

 might be brought forward— (1) The bacteria which have the 

 most flagella become sooner entangled in the tricalcium phosphate 

 coagulum; and (2) the organisms may elaborate substances which 

 are precipitated by the calcium salt. With regard to the first 

 cause, it is to be noted that the amount of calcium necessary to 

 produce a certain effect in the cultures is inversely proportional 

 to the number of flagella on the organisms. The greater the 

 number of flagella, the more firmly will the organisms be retained 

 by the calcium precipitate, and thus less precipitate need be 

 formed to ensure the complete trapping of the bacteria. Another 

 indication might be taken from the observation that the bacteria 

 when living are more sensitive to the action of calcium chloride 

 than when dead. With living cultures complete precipitation 

 was obtained with a certain quantity of salt in one hour, while 

 with dead cultures the same effect was obtained in twenty hours. 

 The steaming requisite to kill the bacteria would undoubtedly 

 shrivel up the flagella. 



The second cause may have much more to do with the pheno- 

 menon than the first. Among the chemical products of the 

 bacteria there are acids, but since the production of acid was 

 limited by the total absence of glucose in the experimental 



