The essentials of practical bacteriology : an elementary laboratory book for students and practitioners / by H. J. Curtis.

  • Curtis, Henry J.
Date:
1900
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Licence: In copyright

Credit: The essentials of practical bacteriology : an elementary laboratory book for students and practitioners / by H. J. Curtis. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    MOSQUITOS AND MALARIA ^45 .„d extend Ross's work. MacCalUun has, amongst British observers, also made important investigations ^^.^^ ^ „,3e of malaria containing the crescent . rof nltue is i sted by ; ^o'quito, the crescents rapidly become spheres. S manrof te^^then throJ out flagella, a process conveniently tenned cfia- ''MiTcallum has demonstrated the fact that in certain birds another malaria] mra Te hreridium) shows similar changes,' but the spherical bodies formed C the c^scent bodies, as described in the case of nian are of two kinds on being hyaline, the other gi'anular, and that only the hyahne spheres proceed to exra-Sion. They are therefore regarded as representing the male element. The flag^'a separate fi-om the hyaline spheres, and, by a wrigghng eel-hke move- ment they at once make for the granular spheres or female element, and at emp tTbo^e their way inside. Only one flagellnm eSects an entrance, and this is followed by a temporary disturbance of the contents of the sphere. • The shape of the sphere subsequently becomes elongated and pointed, or beaked, at one ext;emity, so as to resemble ' the blade of a bix^ad-headed spear The pic^ent collects at the broader posterior end, and the little body point first darts about, and in this way enters a red or white corpuscle. It is spoken of as a travel- Una ^errmcide. By its powers of penetration it can pass out from the blood ingested into the mosquito's stomach through that viscus, so as eventually to give rise to a wart-Uke prommence on its outer surface, projecting into the body cavity of the insect. In this stage it is pigmented and soon acquires a capsule. _ Spindle-shaped filaments, or flageUulse, arise in connection with minute spheri- cal bodies forming within the capsules of the numerous wart-like projections. Finally, on the rupture of the capsules, after from six days to three weeks, the flagellulffi are carried by the blood to the veneno-salivary gland in the head of the mosquito. This gland communicates, by means of a long duct, with the base of the middle stylet or lingula of the mosquito, and in this way the flagellula is injected into the tissues of a bitten animal. The flagellula rapidly develops into the fully foi-med malaria organism, and withm a week or ten days of injection the infected animal shows unmistakable evidence of this, its blood now presenting the charac- teristic parasite. In considering the mode of infection by malaria parasites the following facts, now fully established, should be borne in mind :— (i) They are invariably present, in some form or other, in the disease. (ii) Though they have not been cultivated in the ordinary way, intravenous injection in the blood taken from a patient during an attack of ague produces in a healthy individual a. similar attack ; and there is evidence to show that multiplication of the organism occurs in the blood of the person so treated, though mere contact with a diseased patient never brings about the infection. (iii) A healthy person entering certain regions never previously visited by man may acquire the disease, low-lying marshy districts ' It must be borne in mind, throughout, that the changes described are in the case of malaria blood ingested into the stomach of the mosquito.