PROTOZOA. 3 



and still showing signs of vitality, as may happen in 

 the case of muscular fibre, of vibratile cilia, of 

 spermatozoa, or of zoospores. 



The protozoa are the most widely diffused of all 

 animals. They exist in both running and stagnant, 

 and soft and hard water, in decaying substances, in 

 mosses and confervse, etc. They soon make their 

 appearance in decomposing vegetable or animal 

 matter ; they are found upon the integuments of 

 animals which live in water, and in different 

 organs of the cold, and even of warm-blooded 

 animals. 



The protozoa which live in the organs of animals 

 are true entozoa, for they perish quickly when they 

 are removed from these organs ; and, on the other 

 hand, infusorial animalcules which are accustomed 

 to live in a free state, perish when they are intro- 

 duced into an animal structure. 



The following are the various protozoa which are 

 known to affect the human subject : 



1. Vibriones. — These are extremely minute, fili- 

 form protozoa, which do not possess any visible 

 organization, nor parts suitable for locomotion ; they 

 are multiplied by their transverse division, and move 

 by means of their general contraction. The vibriones 

 are the protozoa which appear first in all infusions, 

 and which, on account of their extreme smallness of 

 size and of the imperfection of our means of observa- 

 tion, must be considered as the most elementary 

 animalcules which are at present known to us. Two 

 genera are included under this head. 



(a.) Genus Bacterium. — The protozoa belonging 

 to this genus are found in various animal fluids when 



B 2 



