ESSAYS ON BACTERIOLOGY. 137 



witli alcoholic eosin. Following the latter method, 

 the blood cells are seen to be red, the bodies of the 

 parasites blue, their nuclei colorless, and the nucleolus 

 dark blue. Probably the most. satisfactory plan is to 

 examine the blood unstained. 



Different varieties of plasmodia have been described 

 as associated with the different types of malaria, but 

 this question, as well as many others concerning the sup- 

 posed malaria] parasite, is still unsettled. Only the diag- 

 nostic value of the organism is generally agreed upon. 



A number of diseases occurring only occasionally in 

 man, the microbes of which are known, may be posi- 

 tively identified by bacteriological methods. Such 

 are glanders, anthrax, and the ray-fungus disease, 

 actinomycosis. Tn a larger number of disorders, of 

 which pneiimonia, cholera, erysipelas and tetanus are 

 types, the identification of the bacteria is occasionally 

 of diagnostic value, though usually such procedures 

 are not called for. It is, however, possible, and with 

 increasing frequency and value, where a well- 

 equipped laboratory is available, to* call bacteriology 

 into service in the diagnosis of infectious or suppos- 

 edly infectious diseases. 



The character -of several disorders, chiefly of the 

 skin, caused by microscopic fungi belonging to the 

 moulds or yeasts, may be established by the micro- 

 scope or by artificial cultivation of the pai'asites. To 

 this group belong ringworm, favus, and the brownish 

 scaly skin disease, tinea versicolor. 



