CHAPTER XV 



Collection of Diseased Tissue 



SELECTION of suitable material for direct examination and culture is 

 most desirable if. one is to elicit information of value. There are several 

 rules of procedure, but one cannot always give directions for the individual 

 case. Here, as in most technical fields, experience is valuable. 



If possible, tissue should be removed from a lesion of recent origin. 

 Since treatment may affect the abundance and the stage of development of 

 the fungus, untreated areas are preferable. The components in the medica- 

 ment may obscure the fungus or confuse the observer by their similarity to 

 fungi; i.e., oil droplets may look like yeast cells. When secondarv infection 

 due to pus-forming bacteria has obscured the primary fungous infection, 

 mild bactericidal therapy for a few days will usually enhance the proba- 

 bility of recovering the fungus. 



Removal of incidental saprophytic fungi from the broken surface of the 

 lesion may usually be accomplished by cleaning with 70 per cent ethyl 

 alcohol. 



If there are many types of lesion, specimens from all should be secured. 

 An abundance of material is usually desirable, but a small quantity of good 

 material is better than a large amount of unselected tissue. 



With ringworm of the scalp the infected hairs should be selected while 

 the patient is observed under filtered ultraviolet rays. Samples of many 

 hairs may be obtained by scraping across the infected patch with a sharp 

 scalpel. The first scrapings are used for direct examinations. Further scrap- 

 ings from this cleared surface are transferred directly to the culture me- 

 dium by cutting into its substance with the scalpel. Filtered ultraviolet 

 rays reveal the sites of tinea versicolor, which may not be readily discerned 

 in daylight. 



When infection results in a porous condition of the nail, the deeper part 

 of the invaded tissue is most apt to contain the pathogenic fungus in pure 

 form. The affected portion of the nail should be cut away; this is advan- 



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