CLASSIFICATION OF ORGANISMS. 21 



rated from their corresponding bacteria. The va- 

 rious infectious agents, including these toxins, find 

 their proper places in the following classification, 

 which, for the most part, is that of von Behring: 



I. Living (i. e.. pathogenic parasites) . 



A. Macroparasites (e. g., intestinal worms, 



pediculi filariae, uncinaria). 



B. Microparasites. 



1. Bacteria (fission fungi: each cell di- 



vides into two in proliferating). 



2. Fungi of more complex organization 



(e. g., aspergillus, oidia). 



3. Protozoa (e. g., Plasmodium mola- 



rice, Amoeba coli) . 



4. Filterable, ultramicroscopic or un- 

 known micro-organisms. 



II. Non-living (i. e., toxins). 



A. Animal toxins (e. g., snake venom). 



B. Vegetable toxins. 



1. Non-bacterial (e. g., abrin. from the 



jequirity bean; ricin, from the cas- 

 tor oil bean: the toxins of hay 

 fever). 



2. Bacterial. 



a. Soluble bacterial toxins (diph- 



theria and tetanus). 



b. Intracellular bacterial toxins, 

 which are not secreted by the 

 cells in a soluble form. 



In the subjects to be considered we shall deal 

 chiefly with microparasites and the diseases which 

 they cause. 



