CHARACTERS OF THE ACT1NOMYCES. 263 



be broken up into little rounded bodies like cocci, so as to 

 give the appearance of a streptococcus, though the sheath 

 enclosing them may generally be distinguished. Sometimes 

 these spherical bodies come to lie free. 



2. Cocci. The formation of these from filaments has 

 already been described, but occasionally young colonies 

 have been found to be largely composed of them, so that, 

 apparently, they multiply by division. Their nature has 

 been much discussed, some observers looking upon them 

 as spores, though for this there does not appear to be suffi- 

 cient evidence. It is better to use the term cocci, and 

 to consider them as constituting a stage in the growth 

 of the parasite in certain conditions. If the view that 

 the parasite is a streptothrix is correct, they are probably 

 to be regarded as conidia. Probably both they and the 

 short bacillary forms can be formed from the filaments, 

 and in turn can develop again into the longer threads. 

 The filaments and cocci are readily stained by Gram's 

 method. 



3. Clubs. These are elongated pear-shaped bodies 

 which are seen at the periphery of the colony, and are 

 formed by a sort of hyaline swelling of the sheath around 

 the free extremity of a filament (Fig. 67). They are usually 

 homogeneous and structureless in appearance. In the human 

 subject the clubs are often comparatively fragile structures 

 which are easily broken down, and may sometimes be dis- 

 solved in water. Sometimes they are well seen when 

 examined in the fresh condition, but in hardened specimens 

 are no longer distinguishable. In specimens stained by 

 Gram's method they are not coloured by the violet, but 

 take readily a contrast stain, such as picric acid, rubin, 

 etc.; sometimes a darkly- stained filament can be seen 

 running for a distance in the centre, and may have a knob- 

 like extremity. In many of the colonies in the human 

 subject the clubs are absent. In the ox, on the other hand, 

 where there are much older colonies, the clubs are practi- 

 cally always present, and are more highly resistant structures 

 than those in the human subject usually are. They often 



