CHARACTERS OF THE ACTINOMYCES 



329 



the sheath enclosing them may generally be distinguished. Rod- 

 shaped and spherical forms may also be seen lying free. 



2. Spores or Gonidia. As occurs in other species of strepto- 

 thrix, some of the filaments of the actinomyces when growing on 

 a culture medium become segmented into rounded spores or 

 gonidia. In natural conditions outside the body these gonidia 

 become free, and act as new centres by growing out into fila- 

 ments. They have somewhat higher powers of resistance than 



FIG. 95. Actiriomycosis of human liver, showing a colony of the 

 parasite composed of a felted mass of filaments surrounded by pus. 

 Paraffin section ; stained by Gram's method and 

 safranin. x 500. 



the filaments, though less than the spores of most of the lower 

 bacteria. An exposure to 75 C. for half an hour is sufficient to 

 kill most streptothrices or their spores; cultures containing 

 spores can resist a temperature from five to ten degrees higher 

 than spore-free cultures (Foulerton). It is probable that some 

 of the spherical bodies formed within filaments when growing in 

 the tissues have the same significance, i.e., are gonidia, whilst 

 others may be merely the result of degenerative change. Both 



