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The capsule now bursts spontaneously, and pours the blasts into the body- 
cavity of the gnat. On drying and staining the blasts are easily seen to be of about 
1 2 to 1 6 /x in length, with a central nucleus, one or two clear oval areas, and tapering 
extremities. No definite movements have been observed in these bodies — possibly on 
account of the reagent (salt solution) which must be used to make them visible in 
fresh preparations. By some means or other, however, they find their way into 
remote parts of the host, and finally pierce the capsule of its salivary gland, enter the 
salivary cells, and lastly the salivary ducts, in all of which situations they can easily be 
seen with the aid of a strong salt solution. From the salivary ducts they evidently 
pass through the insect's middle stylet or tongue into the circulation of a fresh verte- 
brate host, in which it is to be presumed they at once become the amoebulae with 
which the life-history of the parasites commenced. At all events, numerous 
experiments, both on birds and on man, have demonstrated the fact that gnats whose 
salivary glands contain the blasts are capable of establishing infection by their bites 
in the appropriate vertebrate hosts. 
It should be noted that this life-history is in no way a hypothetical one. Every 
fact has been confirmed over and over again by many capable observers. The stages 
in the vertebrate hosts, first established by Laveran and Golgi, have been 
scrupulously studied, and have given rise to a mass of literature already very large. 
The sexual functions of the gametocytes — which can be witnessed in vitro, — originally 
observed by MacCallum, have been seen also by Koch and Marchoux ; while the 
facts are confirmed by the cytological studies of Bignami and others. The develop- 
ment in the gnat and the infection of the healthy vertebrate host by the bite of the 
gnat, originally established by one of us, have been confirmed by Daniels, Koch, 
Grassi, Bignami, Bastianelli, and many others, and are accepted by Laveran, 
Ray Lankester, Metschnikoff, Manson, Celli, and other distinguished men of 
science. A full history of the subject of the relation between malaria and gnats, 
together with a complete bibliography, has been written by Nuttall.* 
The terminology used above was arranged in consultation with Professor 
Herdman, F.R.S. It has been adopted by Laveran and Manson. Grassi and 
others had previously employed the terms gamete and zygote, but used sporozooid 
for the bodies we call blasts. We use the word blast somewhat in the sense employed 
in embryology, and as synonymous with sexually-produced spores. Ray Lankester 
suggests for them the name filiform young. 
It should be added that, within the capsules of mature zygotes large black 
bodies (Fig. 67) are often to be found. It is doubtful whether these have any real 
connection with the parasites. 
* Nuttall, Hygienische Rundschau, numerous papers, 1898, 1899, 1900. Also, On the Role of Insects . . in the Spread 
of Diseases, Johns Hopkins Hospital Reports, Baltimore, vol. viii. 
The most recent figures of stages of the malaria parasites are those published by Koch, Zeitschrift fur Hyg. und Infect., 
1899 (photographs) ; Grassi, Bignami, and Bastianelli, Annali d'Igiene sperimentali, 1899 (plates) ; Sierra Leone Expedition, 
Thompson Tates Laboratories Report, vol. ii. (photographs and drawings). 
