PATHOGENIC BACTERIA. 163 



If possible, examinations for malarial organisms should 

 always be made before quinine is administered. 



Amoeba Dysenteriae. Found in the intestinal ulcers, faeces, 

 and secondary liver abscesses in certain cases of dysentery. A 

 non-pathogenic form, Amoeba coli, also occurs. The Amoeba 

 dysenteric is a unicellular animal organism measuring 25 to 

 35 /j, in diameter, though larger and smaller forms occur. There 

 are a nucleus and a nucleolus ; the protoplasm of the cell-body 

 is vacuolated and often contains red blood-cells and bacteria. 

 In fresh, warm stools active ameboid motion may be observed. 

 The non-pathogenic form is smaller and never contains red 

 blood-cells. 



Small-pox and Vaccinia. The exciting agent of small-pox is 

 still unknown, but numerous bacteria and protozoon-like bodies 

 have been described and given etiological significance by vari- 

 ous authors. There is some evidence in favor of Funck's belief 

 that vaccinia is caused by a protozoon, the Sporidium vaccinale. 

 Animals inoculated with this organism developed both vaccinia 

 and variola. 



Trypanosomes. These are protozoa belonging to the order 

 Jhn/cllata, and have been found in the blood in certain diseases 

 of man and animals. Surra, a fatal tropical disease of horses 

 and mules, the tse-tse fly disease of South Africa, and the 

 sleeping sickness or negro lethargy of the Guinea coast, are due 

 to organisms of this group. It is probable that insects of vari- 

 ous species are the intermediary or definitive hosts of the 

 trypanosome and convey the infection by their bites. 



Texas cattle-fever or bovine malaria is due to an endoglobular 

 parasite, the Pj/rosoma bigeminum, not unlike the malarial 

 organism, and is transmitted through the larvae of the cattle- 

 tick. A similar organism has lately been found to be the cause 

 of the Rocky Mountain fever of man. The infection here also 

 seems to be through the mediation of a tick. 



