280 ESSENTIALS OF ZOOLOGY 



Kadiolaria 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 dis- 

 ease is called trypanosomiasis for the genus name of the animal that 

 causes it, Trypanosoma gamhiense or Trypanosoma rhodesiense. 

 These organisms are transmitted by the tsetse fly, Glossina palpalis, 

 and the disease is limited to that area in Africa where this fly is 

 found. The organisms (Fig. 181) live free in the blood and collect 

 in the lymph glands, spleen, liver, and other organs. In final phases 

 it collects and attacks the brain.' The infection will bring about 

 loss of appetite, severe emaciation, extended coma, which ends in 

 death usually within three or four months, or it may be extended 

 into years. Such animals as antelope, cattle, and some wild game 

 are susceptible to the disease and may serve as carriers. This com- 

 plicates the control of it. The disease has been considered abso- 

 lutely fatal, but recently a drug, arsphenamine, an arsenic com- 

 pound, has been tried with partial success. 



Chagas' Disease. — A closely related flagellate, Trypanosoma cruzi, 

 causes this disease in Central and South America. It is transmitted 

 through the bite of Triatoma, one of the true bugs which is closely 

 related to our common blood-sucking form, the '' kissing bug." 

 Chagas' disease affects dogs, monkeys, guinea pigs, armadillos, as well 

 as man. The symptoms are continued fever; swollen lymph glands, 

 liver, and spleen; anemia; and disturbance of the nervous system. 



Malaria. — The life history of Plasmodium, the sporozoan which 

 causes this disease, has already been discussed under the general topic 

 of Sporozoa. The disease is one of the oldest and most widely dis- 

 tributed among men. It was the flrst disease proved to be directly 

 caused by a protozoan parasite. As early as 1718 a worker by the 

 name of Lancisi ventured the statement that mosquitoes or gnats 

 might transmit malaria ; however, it was not until about the opening 

 of the present century that this relationship was understood. In 1881, 

 Dr. Laveran found a curious parasite in the blood of malaria pa- 

 tients. Several years later Laveran and Manson independently sug- 

 gested that the organism might be transmitted by some blood-suck- 

 ing insect. After several years more of investigation, Major Ronald 



