BLACKWATER FEVER 161 



well-known condition of chronic malaria, or malarial cachexia, 

 common especially in children. The spleen enlargement is the 

 most readily recognizable symptom of chronic malaria and there- 

 fore the " spleen rate," i.e., the percentage of enlarged spleens 

 in a community, gives a fairly accurate measure of the prevalence 

 of malaria to which some degree of immunity has been developed. 

 Usually, unless the weakened condition has given some other 

 disease a chance to put an end to it all, a general improvement 

 ultimately begins. This is especially true in children, so that 

 by the time they reach adult life they are in fairly good health 

 and immune to malaria. 



In the case of sestivo-autumnal or malignant malaria the 

 course of the disease is often not so light, and early death is not 

 a rare occurrence. The fact that the bodies of the malignant 

 parasites clump together and plug the capillaries, thus preventing 

 the proper flow of blood in the vital organs, is probably the chief 

 cause of their malignant nature. One of the most certain symp- 

 toms of a malignant attack of malaria is a total loss of conscious- 

 ness or coma, due to a plugging of the capillaries in the brain. 

 Indeed, 50 per cent of the deaths from malaria are said to be 

 caused by a plugging of the brain capillaries. The type of brain 

 disease which may be caused is very variable but some mental 

 disturbance almost always occurs, and may take place at almost 

 any time during the course of the disease, though it never occurs 

 during the first fever fit, probably because the parasites are not 

 yet numerous enough to do any great damage. 



In connection with malarial fevers there must be mentioned 

 a much dreaded and little understood condition known as " black- 

 water fever." This is a disease in which something destroys 

 the red blood corpuscles in large numbers, causing the coloring 

 matter of the blood, haemoglobin, to be liberated, eventually to 

 be voided with the urine, giving the latter a very dark color. 

 At the same time there is a more or less irregular fever, bilious 

 vomiting and severe aches. In a great many cases it results in 

 death. This disease has usually been considered as an outcome 

 of severe malaria, since it always occurs in malarial countries 

 and usually follows or accompanies an attack of malaria. It 

 is not uncommon in southeastern United States, some parts of 

 tropical Africa, southern Europe and many parts of tropical 

 Asia and the East Indies. In many other malarial districts it 



