290 THE BACTERIOPHAGE AND ITS BEHAVIOR 



that if the infusorial earth after adsorption is washed with some water 

 rendered alkahne with ammonia, the corpuscles are freed into the liquid. 

 This would indicate that the adsorption occurring with this material 

 takes place only if the medium is acid, or at most, neutral. It is sig- 

 nificant that these authors have further noted that filtration through 

 a Berkefeld candle is more readily effected if the medium is alkaline 

 Lq reaction. 



A similar set of experiments authorized Prausnitz and Firle^^^ to state 

 that the amount of adsorption with infusorial earth is practically zero, 

 even if the earth is very fine, and the test is performed with the ma- 

 terials in an alkaline medium. These experiments of Prausnitz are 

 noteworthy, moreover, for their precision, which places them above all 

 criticism. 



Arloing, Langeron, and Sempe-"^ have also found that the degree of 

 adsorption to infusorial earth and to kaolin is essentially negative. 

 In comparison they also report that the corpuscles are adsorbed almost 

 completely by sheep cells freed of plasma, and that the bacteriophage 

 may be found in the sediment after centrifugation. 



According to de Poorter and Maisin^^^ there is a partial adsorption 

 to animal charcoal and to the serum colloids. 



It is well known that when suspensions of colloids of opposite signs 

 are mixed a reciprocal flocculation takes place. Since the bacteriophage 

 bears a negative charge,* a flocculation should not take place when a 

 bacteriophage suspension and a negative colloidal suspension are mixed, 

 but when mixed with a positive colloid flocculation should occur. 



Otto and Munter*^^ have seen that the corpuscles retain all of their 

 properties in the presence of colloidal sulfur (a negative colloid), and 

 certain facts suggest that when in contact with this colloid bacteri- 

 ophagy is favored. Some of my experiments confirm entirely the obser- 

 vations of these authors. 



De Keeker has suggested^^^ that the bacteriophage corpuscles are 

 partially adsorbed by various negative colloids (colloidal preparations 

 of iodine, of manganese, of selenium, of silver, of copper, and of rho- 



* Without going into detail on this point, it may be said that a "micella" is 

 composed of a granule which bears the charge represented by one or two ions, 

 while a layer of ions of the opposite sign is found in the layer of liquid which 

 surrounds the granule. The sign of the colloid is conferred by the nature of 

 the granular charge. For the bacteriophage corpuscle, for example, the granule 

 must bear negative ions (0H~) and in the layer of liquid which surrounds the 

 granule, there must be the opposite, i.e., positive ions (H+). 



