STREPTOTHRICOSIS. 473 



between the different species or varieties. However, in general, all strains 

 are Gram positive to a greater or less degree. 



Differences in acid fast properties have been used as being diagnostic 

 in a number of described species, while unfortunately in others they have 

 not been mentioned. These are important points in differentiation, but 

 unfortunately such properties are a somewhat variable manifestation, 

 depending in part upon the age and environment of the parasite and 

 perhaps also upon other conditions, the nature of which is not clear. As 

 with the oxygen requirements, degrees from the marked acid fast prop- 

 erties of S. eppingeri through those organisms showing the tendency only 

 in certain portions, to 8. madurce' which has no such properties are noted. 

 8. eppingeri, often when taken from animal lesions and sometimes for 

 example in cultures, will show acid fast properties which involve the entire 

 organism, while in other cultures only portions of the organism will 

 retain the fuchsin when decolorized and counter stained with Gabbet's 

 stain. 



Pigment production under certain circumstances is a property of most 

 of the organisms of this group, as the cause of this is unknown and the 

 result is variable, its diagnostic importance is lessened. Under like 

 conditions, the color and general appearance of the pigment in any of 

 these strains is usually fairly constant, but sometimes, particularly in 

 animal tissues, it may show a more intense color. For example, 8. 

 madurce, which usually produces a reddish-pink pigment in cultures, 

 may, when inoculated into monkeys, at one time give a similarly colored 

 pigment or again one considerable darker; so dark in fact as to appear 

 almost black to the naked eye. ■ The pigment of Actinomyces in our 

 cultures shows but little color other than black. On media the color 

 develops slowly and gradually to a dark gray, almost black. Some of the 

 phenomena of pigment production and color ma) r be explained, but in gen- 

 eral the process is still obscure. For example, a darker pigment usually 

 results in animals from the inoculation of fresh material from another 

 animal than is the case if cultures are used. The next lighter shade is 

 produced by inoculation with old, pigmented cultures, but color produc- 

 tion is slower when young, unpigmented cultures are used for inocula- 

 tion. Early pathologic lesions due to these parasites, like young cultures, 

 rarely show pigment. The later in both instances is produced and grows 

 more marked with age. Concentration undoubtedly has something to 

 do with the apparent color of the pigment, for the harder the granule 

 the darker the pigment appears to be. 



Granule formation both in tissues and to a less extent, in cultures, is 

 a property of all the pathogenic Streptotliricce with which we have worked. 

 These granules vary considerably in consistency and color in the several 

 species, but in the majority of instances they are made up of branching 

 filaments with transformation products, which consist in irregular forms, 



