230 PATHOGENIC MICROORGANISMS. 



greatest importance is the Trypanosoma gambiensis, the etio- 

 logical factor in sleeping sickness. It is a little shorter 

 and thicker than T. lewisi a'nd T. brucei. It measures from 

 20-25 fj. long and 2-3 //. in width. In life it has a slow undu- 

 lating movement. Its flagellum extends from the centrosome 

 through the body, curving around the nucleus and extending 

 beyond the nucleolus at the anterior end. The nucleus is oval 

 and central. The Trypanosoma gambiense is conveyed to man 

 by the bite of the tse-tse fly (Glossina palpalis). The trypan- 

 osomes are stained by the Wright or other blood-stains. 



Leishmania Donovani. 



In certain forms of fever of irregular character and sup- 

 posed to be of malarial origin, Leishman and Donovan, work- 

 ing independently, found certain protozoal organisms which 

 they considered the etiological factors. 



Morphology and Staining. The Leish man-Donovan bodies 

 are small elliptical or circular bodies 2-3 /j. in diameter, and 

 contain chromatin. This is arranged in a small rod-shaped 

 portion and a larger surrounding circular portion. The chro- 

 matin is usually arranged in the short axis of the ellipse. To 

 demonstrate this organism, it is generally necessary to obtain 

 blood by puncture of the liver or spleen. The organisms are 

 usually found either singly or in bunches free in the blood 

 of these organs. For staining, Wright's stain may be used. 

 The Leishman stain gives splendid results, as well as any of 

 the Romanowsky modifications. By Wright's stain the chro- 

 matin is colored dark blue, the rest of the organism is stained 

 a paler blue. 



Distomum Hsematobium, 



first described by Bilharz, causes a disease found in Africa 

 and Arabia, characterized by anaemia, emaciation, and haemor- 

 rhages from the bladder and rectum. The adult male worm 

 measures about 12 m.m. long and 1 m.m. broad. The female 

 is much longer and thinner, and in copulation is received into 

 a groove in the body of the male. The ova are discharged 

 into the blood and lodge in the capillaries of the rectum and 

 bladder and elsewhere. They are discharged at times in the 



