112 PROTOZOAN PARASITISM 



some distance below the tartar adjacent to the 

 cementum. They do not invade the gingival or bony 

 tissues but the latter between the teeth and below 

 the level of tartar formation is extensively absorbed. 

 This report expresses the observation of the present 

 writer in failing to find invasion of the tissues by 

 the amoeba. 



Kofoid (1929) develops a very pretty chain of 

 argument from his studies, leading to the inference 

 of a part in the events of pyorrhoea alveolaris played 

 by Endmnoeha gingivalis. In the first place is the in- 

 fection by leptothrix and other filamentous bacteria, 

 as a basis for the tartar formation by their calcifica- 

 tion. Next comes the amoebic infection which is 

 able to maintain itself on the fringes of the tartar 

 calculus. There the amoebae consume leucocytic 

 nuclei and excrete from these nucleo-proteins, phos- 

 phorous, available for deposit in the tartar as calcium 

 phosphate. The bone of the adjacent teeth is re- 

 sorbed near the site of the deposit of the calcium 

 carbonate and phosphate by some unknown process. 

 Thus one is led to suspect the triad, bacteria, 

 amoebae, calculus, against which the more successful 

 dental measures of instrumentation and surgery in 

 the treatment of pyorrhoea may be directed, although 

 unconsciously. 



The amoeba not only ingests nuclear remnants of 

 pus cells but it may consume red blood corpuscles 

 (Smith and Barrett, 1915, and Howitt, 1925) and may 

 even haemolyze these elements without ingesting 



