ItwaspracticedbytheBakwainsatatimewhentheyhadnointercourse，directorindirect，withthesouthernmissionariesTheyalladoptreadilytheuseofvaccineviruswhenitisbroughtwithintheirreach。
Acertainloathsomedisease，whichdecimatestheNorthAmericanIndians，andthreatensextirpationtotheSouthSeaIslanders，diesoutintheinteriorofAfricawithouttheaidofmedicine；
andtheBangwaketse，whobroughtitfromthewestcoast，lostitwhentheycameintotheirownlandsouthwestofKolobeng。
ItseemsincapableofpermanenceinanyforminpersonsofpureAfricanbloodanywhereinthecentreofthecountryInpersonsofmixedblooditisotherwise；andthevirulenceofthesecondarysymptomsseemedtobe，inallthecasesthatcameundermycare，inexactproportiontothegreaterorlessamountofEuropeanbloodinthepatient。
AmongtheCorannasandGriquasofmixedbreeditproducesthesameravagesasinEurope；amonghalf-bloodPortugueseitisequallyfrightfulinitsinroadsonthesystem；butinthepureNegroofthecentralpartsitisquiteincapableofpermanenceAmongtheBarotseIfoundadiseasecalledmanassah，whichcloselyresemblesthatofthe`foedamulier’ofhistory。