190 DISEASES DUE TO PROTOZOA 



pushing out of a part of the cell wall like a bud; this is the 

 pseudo-pod or false foot. This means of progression enables 

 the organism to penetrate intact mucous surfaces and pass 

 through sand filters impermeable for bacteria. 



The Entameba histolytica is an irregularly shaped mass of 

 simple protoplasm with a primitive structure. Its nucleus 

 is usually single in contrast to other amebse. It measures up 

 to g-J-Q inch. It moves and embraces its food by the pseudo- 

 pods. It reproduces by division or by the production of 

 daughter cells within its body. When these are massed 

 together and held by a capsule, it is said to be encysted. 

 When such cysts are taken into the body the intestinal juices 

 probably dissolve the capsule and let the cells go free. Encyst- 

 ment occurs when conditions for life become unfavorable. 

 Amebse are not killed by cold, but succumb to 60 C. or 140 

 F. in one hour. Acids are unfavorable for the growth. They 

 are cultivated artificially with great difficulty, and are usually 

 combined with bacteria, in whose presence they multiply 

 without hindrance. Only monkeys and dogs are susceptible 

 to the amebse causing disease in man. No therapy depending 

 on antitoxins or vaccines is practicable. 



MASTIGOPHORA. 



Kala-azar. In the next group of protozoa, the flagellata, 

 several are pathogenic for man. Kala-azar is a peculiar, 

 slow disease, called by various names, depending upon its 

 locality dumdum fever, kala-azar, etc. exhibiting a large 

 spleen, hemorrhages, anemia, and fever. The causative 

 microorganism may be found almost anywhere in the body, 

 but chiefly in the spleen, whence it may be obtained by 

 puncture with a needle. It is said that fleas, bed-bugs and 

 mosquitoes transmit the disease. The protozoon responsible, 

 Leishmania Donovani, is an ovoid or circular or comma- like 

 mass with two nuclei, and one moderately long flagellum on 

 the forward end. They are from TT^ or to suW inch long 

 and about two- thirds as wide. (See Fig. 60.) 



