78 TEXTBOOK OF ZOOLOGY 



chain including water fleas, larger crustaceans, and fish. Too, the 

 protozoans are not classed as predators on man as would be the 

 lion, but many of them are parasites. Many diseases of man and 

 animals are caused by Protozoa. Most of the diseases of this origin 

 are more prevalent in the tropical and subtropical regions of the 

 earth. Such diseases may attain sufiScient importance to render 

 large portions of continents uninhabitable by man ; for example, 

 much of northern South America and Central America was, at one 

 time, ruled by yellow fever and malaria, and the same applies for 

 sleeping sickness in Africa. There are other Protozoa that render 

 water unfit for drinking or help fertilize the soil. 



Amoebic Dysentery. — Ulcers on the inside of the walls of the 

 intestine of man are caused by this disease. There results from 

 this, severe diarrhea and dysentery. From the intestine the infec- 

 tion, if allowed to continue, will be carried to the liver where 

 serious abscesses are formed. The infection is usually obtained 

 directly through drinking water or eating food which has been 

 contaminated with the encysted organisms from fecal matter. About 

 10 per cent of our population are said to be carriers of these organisms. 

 The causal agent is one of the Amoebae, Endamoeba histolytica (see 

 Fig. 391), and it can be rather successfully eliminated from human 

 beings by use of such drugs as emetine, carbarsone, and chiniofon, 

 administered by a physician. Some other Amoebae have been found 

 in human beings, but, so far as known, they are not pathogenic. End- 

 amoeba coli, Endolimax nana, and Endamoeba gingivalis are such 

 examples. 



Foraminifera which is an order in class Sarcodina has some eco- 

 nomic importance because of the limestone which is formed by the 

 concentration of the material of the dead tests or shells. A genus 

 by the name of Globigerina is one of the best known members of the 

 group. It is about the size of a pinhead, and as it dies, it sinks to the 

 bottom of the ocean where the mass forms the globigerina ooze which 

 hardens into solid chalk. 



Badiolaria is another order in the same class. Each of its repre- 

 sentatives has a complicated skeleton of silica. From their skeletal 

 remains comes an ooze on the sea floor sometimes hundreds of feet 

 deep. From this is formed quartz or flint. 



African Sleeping Sickness. — This malady is the most important 

 disease of man caused by flagellate Protozoa. Technically the disease 



