194 l'KOl!LEMS AND PRINCIPLES OF .MALARIA PREVENTION. 



favoural)lc circumstances each one of the young ])arasites again 

 enter- a retl l)loo(l cell, grows, sulxlivides. and bursts a cell. 

 Thus the cycle is kept up practically indefinitely. Now, the 

 periodical ])aroxysms of the disease called malaria coincide 

 exactly with the time when a number of parasites rupture the 

 red Ijlood corpuscles containing them and are scattered into the 

 circulation. This freeing of the young parasites is also pro- 

 bably coincident with a release of certain toxins. The parasite 

 causing (|uartan malaria requires '/2 hours for each cycle in the 

 human host. The parasite causing the tertian type requires 48 

 hours, and the parasite of the sub-tertian type 48 hours or less. 



It is possible for one person to be infected with two or all 

 of the three species of the Plasmodia, and to be infected with 

 several strains of one species. In either case the periodicity 

 of the paroxysms is, of course, correspondingly modified. 



So far as it is known up to the present, only mosquitos of 

 the genus Anophelinre are capable of transmitting the plasmodium 

 of malaria to man, and it has also been found that certain species 

 of this genus are incapable of transmitting malaria. In fact, up 

 to the present only the following species of Anophelinre have 

 been demonstrated as being capable of transmitting malaria : — 



Anopheles iiiaciilif^ciinis Meigen. t8i8. Europe and Xnrtli America. 



Anopheles hifiireatiis Linn.-eus. 1758. Europe. 



Anopheles pseiidopuiiefipennis Darling. 1910. Panama. 



Anopheles tarsiniaculata Darling, 1910. Panama. 



Anopheles (?) fonnosaensis Tsw/.nVi, 1902. Formosa. 



Cellia albimana Wiedemann, 1821, West Indies and South .\nierica. 



Cellia argyrotarsis Robincau-Desvoidy, 1827. America. 



Cellia pharoensis Theobald, 1901. Africa. 



Myzoniyia listoni Liston, 1901. India. 



Mycomyia fiincsta Giles. 1900. West Africa. 



Myzoinyia hispaniola Theobald, 1903. Spain and North Africa. 



Myaoniyia turkhndi Liston, 1901. India. 



Myzorhynchns harhlrostris Van der Wulp. Asia. 



Mycorhynchus sinensis Wiedemann, 1828. Asia. 



Myzorkynchus umbrosiis Theobald, 1903. Malav States. 



Nyssorhyiichits aiinulipcs Walker, 1850. .Australasia. 



Nyssorhynchits fuUgiiiosits Giles, iyo(j. Asia. 



Nyssorhynclms macnlipalp's Giles, 1902. Africa and .Asia. 



Nyssorhynchns stepheiisi Liston, 1901. India. 



Nyssorhynclms thcobaldi Giles, 1901. India. 



Nysso lily nc hits wilUnori James, 1904. Asia. 



Pyretophorus costalis Loew, 1866. West Africa. 



Pyrctophorus supcrpictus Grassi, 1900. Europe, Africa, and Asia. 



Pyretophorus chaudoyei Theobald, 1903. Africa. 



Pyretophorus uiyzomyifacies Theobald, 1907. Algiers. 



But even where the species of Anophelinae demonstrated 

 as being capable of transmitting malaria are present, it does not 

 necessarily follow that malaria exists in the locality, for it is 

 necessary that human malaria carriers be also present. For 

 example, in England three species of Anophelinae are present — 

 A. maculipcnnis, A. bifurcatus, and A. nigripes. The first two 

 are known positively as carriers of malaria, and yet England is 

 practically free from the disease. 



It is known that both a certain number of human carriers 



