The Parasitology of Pyorrhoea alveolaris. 195 



the so-called Valilkampfia type, and also appears to have some 

 affinities to paramoeba. We would, however, suggest that this 

 particular species may be described as a semi-parasite, that is to 

 say, a free-living form which has become adapted to anaerobic life 

 in the pockets, and has been partly modified thereby. 



We consider that this is a reasonable suggestion for the 

 following reasons. As observed in the mouth the amoeba corre- 

 sponds to the parasitic amoebse in possessing no contractile vacuole. 

 It can grow, and indeed grows best, at a temperature of 37° C. It 

 can develop in strictly anaerobic conditions, under which no free- 

 living form tested would grow well. The entire absence of the 

 contractile vacuole in the amoebee as seen in the mouth, and its 

 presence in cultures, unless made under strictly anaerobic condi- 

 tions, is very important. The contractile vacuole in the protozoa 

 has usually been regarded, though without much proof, as an 

 excretory organ, somewhat in the nature of a rudimentary kidney, 

 and these experiments appear to prove this view and to show 

 why the parasitic forms do not possess such an organ. The end 

 product of proteid disintegration and oxidation is usually urea, 

 or bodies allied to it. Now in protozoa, living under aerobic 

 conditions, oxidation may be fairly assumed to produce considerable 

 quantities of such waste products, and hence the need of a special 

 organ for their elimination. In protozoa, living a parasitic life, 

 however, under anaerobic conditions, it is evident that oxidation 

 must be reduced to a minimum, and the need for a contractile 

 vacuole, therefore, does not exist. On no occasion have definite 

 cysts been observed in preparations taken from the mouth, but we 

 have twice seen forms that were either amoebae in an early stage 

 of encystation, or cysts themselves, but it was exceedingly difficult 

 to feel certain of the point. That encystment, if it occurs at all in 

 the pockets, would be extremely rare is shown by the fact that 

 encystment is very long delayed under strict anaerobiosis, and 

 may not occur at all. We would suggest the name Amoeba huccalis 

 for this species, the parasitic type being known as Entamceba 

 gingivalis. 



Having obtained pure cultures, Dr. Penfold suggested that it 

 might be possible to produce a specific lysing serum, either for 

 the cysts or for the amoebae. He therefore injected a series of 

 rabbits intravenously, and another series subcutaneously, with a 

 strong suspension of cysts killed by heating to 56° C. in normal 

 saline. After two such injections, four more inoculations were 

 made, using suspensions of living cysts. In the case of the rabbits 

 receiving intravenous injections no effect was observed, whilst in 

 those inoculated subcutaneously, swellings were formed which 

 contained a thick pus. This pus was found to contain cysts 

 in the living condition, and cultures were obtained. Samples 

 of the blood were tested from time to time, but no particular 



