470 THE PROTOZOA 



THE CHLAMYDOZOA. 



The name Chlamydozoa of Prowazek (Strongyloplasmata, Lip- 

 schiitz) was proposed in order to include in the first place a class of 

 highly problematic organisms believed to be the causes of certain 

 diseases of man or animals. It is not yet certain exactly what 

 diseases are to be referred to Chlamydozoa. According to Hart- 

 maim (909), undoubted chlamydozoal diseases are vaccinia and 

 variola, trachoma, and molluscum contagiosuni, amongst human 

 beings, and in birds epithelioma contagiosum and diphtheria. 

 Further diseases probably attributable to Chlamydozoa are hydro- 

 phobia, scarlet fever, measles, foot-and-mouth disease of animals, 

 and " Gelbsucht " of silkworms. In all these diseases the virus has 

 certain common properties, while exhibiting specific peculiarities 

 in each case. It can pass through ordinary bacterial filters without 

 losing its virulence, and it produces characteristic reaction-products 

 or cell-inclusions in the infected cell. 



In order to understand why these organisms should be men- 

 tioned in a book dealing with Protozoa, the subject is best dealt 

 with in an historical manner. The advances in the knowledge of 

 the diseases mentioned may be summarized briefly in four principal 

 stages : 



1 . Various investigators at different times have made known the 

 existence of peculiar cell-inclusions in the infected cells in a certain 

 class of diseases, inclusions which have been known by the names 

 of their discoverers for instance, in trachoma (Prowazek's bodies), 

 vaccinia (Guarnieri's bodies), scarlet fever (Mallory's bodies), 

 hydrophobia (Negri's bodies), etc. 



2. By many investigators the characteristic cell-inclusions were 

 identified as the actual parasitic organisms causing the disease. 

 They received zoological names, were referred to a definite position 

 in the ranks of the Protozoa, and attempts were made to work out 

 and construct a developmental cycle for them. The supposed 

 parasites of molluscum contagiosum were referred to the coccidia ; 

 those of vaccinia and variola were given the name Cytoryctes ; of 

 hydrophobia, Neuroryctes ; of scarlet fever, Cydasterium. 



Calkins (908) studied in great detail the cell-inclusions of vaccine 

 and smallpox, and described a complete developmental cycle, in its 

 main outlines as follows : The primary infection is brought about, 

 probably, at some spot on the mucous membrane of the respiratory 

 or buccal passages by air-borne germs (spores). After active pro- 

 liferation at the seat of the primary infection, the parasites are 

 carried to all parts of the body in the circulation, probably during 

 the initial fever. These two early phases are hypothetical. The 

 third phase is the appearance of the parasites in the cells of the 



