CULTURE MEDIA 681 



Sahli's borax blue. 



Distilled water, - 40 parts. 



Saturated aqueous solution of methylene blue, - 24 



5 per cent, solution of sodium borate, - 15 



After staining, the preparation is differentiated in absolute alcohol, washed 

 in xylol and mounted in balsam. 



An hanging-drop preparation is the best method of studying the cultural 

 characteristics of the parasites. 



Place a drop of culture fluid on a slide, sow it with the parasite and then invert 

 the slide on a Bcettcher cell in such a way that the fluid is within the ring, and lute 

 with paraffin. Incubate for 5 or 6 days and then examine under the microscope. 

 To make a permanent preparation, after examining in the living state lift the slide 

 from the cell, dry, fix with a drop of pure acetic acid, wash and stain with an aqueous 

 solution of eosin. Wash. Dry. Mount in balsam. 



2. Cultures. The Tricophyta are strictly aerobic. Growth occurs at 

 laboratory temperature but is more rapid at 33-35 C. ; at the higher 

 temperatures, however, the culture soon becomes old and the morphology 

 of the parasites is altered. Primary cultures are best made at the tempera- 

 ture of the laboratory. The Tricophyta cannot be cultivated on acid media. 

 They grow readily on potato but best on media containing sugar and a little 

 nitrogenous matter, and particularly well on beer- wort (180 per 1,000 of 

 maltose), and the following solution (Sabouraud) : 



Sabouraud's proof medium. 



Crude maltose (Chanut), - 4 grams. 



Granulated peptone (Chassaing), - 0*75 to 1 gram. 



Distilled water, - - 100 grams. 



Sabouraud's medium may be solidified by adding T5 parts of agar per 

 cent. 



[In artificial culture the ringworm parasites are subject to great morpho- 

 logical variation both microscopical and macroscopical. So considerable are 

 these pleomorphic changes that unless the fact be borne in mind a given 

 species may easily be mistaken for another species of the same, or even of a 

 different, genus. Once a culture has undergone a morphological variation 

 there is no known method by which it can be made to reassume its original 

 characteristics. To avoid as far as possible pleomorphic changes taking 

 place in cultures Sabouraud advises the use of a medium containing no sugar 

 on which to cultivate stock cultures. The medium is of the following com- 

 position : 



Sabouraud's medium for stock cultures. 



Distilled water, - - 100 grams. 



Granulated peptone (Chassaing), - - 3-5 ,, 



Agar, T8 grams.] 



The isolation of the parasites. A diseased hair, the contents of a vesicle 

 of tinea circinata, or a few drops of blood from the site of one of the lesions, 

 all afford suitable material from which to isolate the ringworm parasites. 



(i) Cultures from blood. Cleanse the skin of the affected part and after 

 lightly scarifying it collect a few drops of blood and spread the material on 

 sloped tubes of Sabouraud's maltose agar. 



(ii) Cultures from vesicles. Adopting the necessary precautions to avoid 

 contamination, remove the contents of a vesicle with a fine pipette or a 

 platinum loop and sow the material on tubes of the same medium. 



(iii) Cultures from hairs. The parasite does not occur in pure culture in the 

 lesions of ringworm, but is always mixed with five or six other species of 



