SCHIZOPHYTA— SCHIZOMYCETES 165 



poisonous contents of the cells are liberated and then go into solution. They 

 may be liberated, also, by grinding the bacteria, and extracting with water. 

 These poisonous protoplasmic substances have been called toxalbumins, but this 

 term commits one to the supposition that all of this type of poisonous sub- 

 stances are proteid in nature. This has been by no means proven, consequently 

 the term endotoxins is to be preferred. 



The following terms used in discussions of immunity will need defining. 



An Antitoxin is a substance capable of neutralizing a toxin by combining 

 with it, and is produced in the animal body as a reaction to the introduction of 

 a toxin in non lethal doses. 



A Bacterial Agglutinin is a substance produced in the animal body as a re- 

 action to the presence of certain bacteria or their products. When introduced 

 into a suspension of the organism the agglutinin will cause the bacteria to clump 

 (agglutinate) into groups. 



A Bacteriolysin is a substance produced in the animal body as a reaction 

 to the presence of bacteria or their products which will destroy and dissolve 

 the corresponding (homologous) organisms. 



An Opsonin is a substance found in the blood serum which will unite with 

 bacteria and render them positivelj'^ chemotactic for the white blood cells. This 

 preliminary union of opsonin and bacterium seems to be necessary before en- 

 gulfment and destruction of the bacteria by the white blood cells can take place. 



In discussing the specific effects and products of the various species of 

 bacteria, there would be an advantage in grouping these bacteria, according to 

 the substances produced, and their effect upon animals and man. However, 

 that this portion may be in keeping with the remainder of the text, the specific 

 effect will be discussed and noted under each organism, and the organisms put 

 in their correct place in the genera of Migula's system of classification. In many 

 instances, bacteria not closely related produce effects that are very similar; 

 in some of these cases, the discussion will be under the first of that group 

 reached, the remainder of the group will contain simply the reference to the 

 form under which the discussion is given. 



COCCACEAE 



Organisms globose or spherical in a free state, not elongated in any direc- 

 tion before division into one, two, or three planes, when united in pairs or 

 groups, sometimes flattened on the proximal sides, containing five genera, three 

 of which are of importance from our point of view. 



BACTERIACEAE 



Cells cylindrical or oval, dividing only in one plane, cells straight, rod- 

 shaped, without sheath, either non-motile or motile, by means of flagella ; con- 

 tains three genera. 



SPIRILLACEAE 



Cells cylindrical, dividing in one plane, not straight, being bent or spiral, 

 and without sheath; contains four genera. 



CHLAMYDOBACTERIACEAE 



Cells cylindrical, dividing in only one plane, enclosed in a sheath; contains 

 five genera. 



