CHARACTERS OF THE ACTINOMYCES 



319 



the sheath enclosing them may generally be distinguished. Rod- 

 shaped and spherical forms may also be seen lying free. 



2. Spores or Gonidia. Like other species of streptothrix, the 

 actinomyces when growing on a culture medium shows on its 

 surface filaments growing upwards in the air, the protoplasm of 

 which becomes 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 filaments. They 



Flu. 91. Actinomycosis 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 with 

 safranin. x 500. 



have somewhat higher powers of resistance than 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 the 



