NOMENCLATURE 135 



will have a most serious effect upon the welfare of 

 the body. 



Befofe Laveran's discovery, Lankester had described 

 a parasitic organism living in the blood-cells of a frog, 

 and within the last twenty years numerous other 

 organisms have been discovered and described by 

 various investigators living in the blood-corpuscles 

 of reptiles, birds, monkeys, and bats. There are at 

 least three species of Haematozoa, as they are called, 

 which live in the blood of man, and these three 

 correspond to the three kinds of malaria the tertian, 

 the quartan, and the aestivo-autumnal, or, as it is 

 often termed, the irregular type of malarial fever, 

 which occurs so frequently in the late summer and 

 autumn in Italy and elsewhere. The haematozoon 

 causing the last-named fever has been especially 

 studied by the Italian observers, and it differs more 

 markedly from those causing the tertian and quartan 

 fevers than the latter do inter se. It is not universally 

 conceded that the differences between these three 

 forms of organism are such as to establish a difference 

 of species, but the weight of opinion is in favour of 

 this view. Ross even places the parasite of the 

 aestivo-autumnal fever in a separate genus, and we 

 have throughout this article adopted his nomenclature. 

 Zoologically he groups all the three species infesting 

 man in Wassielevski's family Haemamcebidae, which, 

 besides the human parasites, includes a species found 

 in monkeys, three species in bats, and two in birds. 

 The species causing tertian and quartan fevers are 

 grouped by Ross in the genus Hcemamceba, the former 

 being called Hcema^nwba vivax, the latter Hcemamaba 

 malarice. The parasite causing the aestivo-autumnal 

 fever is called Hcemomenas prcecox. 



With the exception of a few details the life-history 

 of all these forms is practically identical, although the 

 time which is occupied by different phases of their 



