376 MICROBIOLOGY 



tain protozoa. Novy and Knapp 4 have cultivated flagellates, 

 occurring in the blood in the condensation fluid of blood agar. 

 According to Park, certain ameba may be cultivated in the 

 following way : From the material containing ameba a loopful 

 is removed with a platinum wire and drawn over the surface 

 of the following medium poured in sterile petri dishes : Agar 

 one part, tap water 90 parts, ordinary nutrient broth 10 

 parts, mixed and sterilized in the regular way. 



Protozoa are studied microscopically in the fresh condi- 

 tion by spreading the material containing them on slides. The 

 oil immersion objective is required. Permanent preparations 

 are made by allowing smears to dry and then fixing in some 

 fixing solution, rather than heat as for bacteria. Schaudinn 

 recommended hot (50 C.) alcohol sublimate or saturated 

 sublimate to which 5% glacial acetic acid has been added. The 

 preparation should remain in it a few seconds and then it 

 should be washed one-half hour in 60% iodine alcohol and 

 then placed in 10% alcohol. They are then rinsed in water 

 and stained. For this the bacterial stains may be used, also 

 thin Delafield's hematoxin, picro-carmine, Mallory's eosin 

 methylene blue and others. 



Protozoa are affected injuriously by heat, electricity, 

 light, moisture and chemical disinfectants. They may live in 

 intense cold for a long time but most of them are destroyed by 

 a moderate heat. Rather strong induction shocks will kill 

 most protozoa. When protozoa are encysted while drying they 

 will endure long periods of dessication. They are destroyed 

 by disinfectants. 



Pathogenesis. The diseases producing protozoa perform 

 their harmful action either mechanically or by the direct 

 destruction of the special tissues which they find suitable for 

 food. As a rule, so far as known, they do not produce toxic 

 substances. Infection with protozoa is often accompanied by 

 some of the lower forms of animal life, acting as intermediate 

 hosts or direct carriers of the organism. 



4 Novy and Knapp. Jour. Am. Med. Asso., Vol. XLVII (1906) p. 

 215. Also Science, Vol. XXV (1907) p. 815. 



