THE PATHOLOGY OF MALARIA 599 



in native adults in malarial districts, this is only true of those 

 born in the locality, natives coming from neighbouring non- 

 malarial districts into the malarial region being liable to contract 

 the disease. At present it must be held that the facts available 

 do not enal tie us to determine the relative parts played by the 

 development of artificial immunity on the one hand, and the 

 existence of a natural immunity on the other, in apparent 

 insusceptibility to malaria. 



Our knowledge on the relationship of blackwater fever to 

 malaria is also in an unsatisfactory condition. Blackwater fever 

 is a condition often occurring, especially in Europeans, in tropical 

 countries. It is characterised by pyrexia, darkly-coloured urine, 

 the colour being due to altered haemoglobin pigment, delirium 

 and collapse, frequently ending in coma and death. By some 

 the condition has been looked on as a separate disease, by others 

 as the terminal stage of a severe malaria. With regard to the 

 former view no special parasite has yet been demonstrated. 

 Stephens sums up the evidence for the second view by saying 

 that malaria, apart from the occurrence of blackwater fever, is a 

 relatively non-fatal disease; that in the great majority of cases 

 there is direct or indirect evidence of the subject of the condition 

 having suffered from repeated attacks of malaria ; that while in 

 all cases there must be an agent at work causing ha3molysis, 

 there is evidence that in many cases there is the possibility of 

 that agent being quinine. In a recent important work, Christo- 

 phers and Bentley come to the conclusion that the essential 

 feature in blackwater fever is an extra-cellular destruction of 

 red corpuscles in the blood plasma, a lysaemia as they call it, 

 but that this is not directly due to parasitic, osmotic, or chemical 

 actions, but to a specific haemolysin arising in the body as the 

 result of the repeated blood destruction. They have shown, for 

 example, that the addition of fresh serum (complement) to the 

 red corpuscles of blackwater fever, as well as of malarial, patients 

 may produce lysis, this apparently being due to a substance 

 corresponding to immune-body united to the corpuscles in 

 qui'stion. The development of this haemolysin (autolysin) results 

 from the extensive and repeated destruction of red corpuscles by 

 the malarial parasite. Thus though the latter is not the 

 immediate cause of the lysaemia, which is the essential feature of 

 l>laekwater fever, it is the means of inducing the development 

 of the haemolysin. If this view of the process is found to be 

 i oiroct, it would of course explain the relationship of malaria to 

 the condition. They also consider that in the conditions men- 

 tioned, i.e. where there has been repeated destruction of an 



