Microhic Diseases Individually Considered. 273 



three hundred diameters will always prove sufficieut 

 for the recognition of the parasites. 



This mode of preparaton, however, is inadequate 

 for the detailed study of the fungus. The center of 

 the radiating masses is nearly always calcified, and 

 this transformation conceals its filamentary structure 

 and, at the same time, prevents the dissociation of the 

 tuft. The latter is also enveloped by a mucoid, viscid 

 substance which tends to hold together the enlarge- 

 ments at the periphery. The inconvenience arising 

 from these two circumstances is obviated by treating 

 the substance to be examined with alkalies or dilute 

 acids. 



For this purpose we have found the employment 

 of dilute ammonia quite satisfactory ; the sand-like 

 grains yet require to be crushed in order to spread, or 

 better, to dissociate them. 



By this means beautiful preparations are obtained 

 in which the mycelium and its connection with the 

 conidia can be studied. 



The examination of sections is highly instructive. 

 The actinomyces can be stained in diiierent ways. 

 According to the way which is mostly recommended, 

 the sections are immersed in a solution of orseille,(l) 

 then in alcohol, and, finally, in an aqueous solution 

 of gentian violet or methylene blue. A double stain- 

 ing is thus obtained, the conidia being red and the 

 mycelium violet or blue. 



In our opinion Weigert's method gives better re- 

 sults. The antioomyces take a violet color and the 



(1) Pure orseille, free from ammonia, dissolved until a deep red 

 color is produced, iu : acetic acid, 5 ; absolute alcohol, 20 ; water, 40. 



