l8 THE CYTOLOGY AND LIFE-HISTORY OF BACTERIA 



antibodies against chemically dehncd tractions ot (e.^.) the bacterial capsule. 

 When these antibodies are allowed to react with bacteria which contain the 

 appropriate chemical fraction, in the field ot the phase-contrast microscope, 

 the antigen-antibody combination shows clearly in dark contrast ; presumably 

 because of the coagulation of the antigen. By this means the capsule of certain 

 Bacillus species has been demonstrated to consist of narrow lamina of poly- 

 saccharide and polypeptide elements, with larger masses of polysaccharide 

 at the poles of the bacilli, and at the cross-walls. The cell wall can also be 

 made visible when it reacts with the homologous antibody. 



Non-specific proteins will also enter into a salt-like combination with 

 capsular components at appropriate values ot pH, rendering them visible by 

 phase-contrast microscopy. 



These methods can be used with even greater success if the structures arc 

 separated by partial digestion with such enzymes as lysozyme or trypsin. 



The further development of these techniques, by the use of antibodies 

 specific for cytoplasmic and nuclear components others a most promising 

 field for study in the cytology of bacteria and other cells also. 



These papers should be read in the original for full descriptions ot this 

 elaborate technique. 



Fig. 6 

 DEMONSTRATION OF CAPSULES BY TOMCSIK'S METHOD 

 These photomicrographs were made by Tomcsik's method for specific demonstration of 

 antigenically active material by phase-contrast microscopy. The reaction of the antigen 

 in situ with the antibody prepared against a chemically defined extract or suspension renders 

 the structure in question visible to phase-contrast, and gives a simultaneous demonstration 

 of its form and chemical composition. All plates are of a capsulated species of Bacillus < 2500. 



(1) Capsulated bacteria without added antibody. 



(2) The same, with the addition of an antibody active against the polypeptide fraction of 

 the capsule. 



(3) The same field as (2) with the further addition of an antibody active against the 

 polysaccharide fraction. 



It will be observed that the untreated capsule shows only as a diftuse, pale zone ; after 

 the addition of the polypeptide antibody it appears clearly defined but homogeneous, but 

 the addition of the polj'saccharide antibody reveals an unsuspected striated structure, with 

 larger dark areas at the poles and points of division. 



(4, «i) Originally non-capsulated bacteria which have developed a secondary capsule in a 

 centrifuged deposit at room temperature. Polysaccharide antibody reveals exceptionally 

 thick capsular septa, occasionally splitting in division. 



(5, 7) The same as (4, 6) demonstrated by polypeptide antibody. In this case the poly- 

 saccharide septa appear as gaps in the capsule. 



