Most important results in this field have very recently been obtained by Big nami (Lancet, Dec. 3, 10, '98), whose in vestigations have proved conclusively that at least the most important method of transmission of malarial infection is by inoculation through the agency of the inosquito. Bignami's earlier experiments yielded only negative results, and experi ments conducted as recently as August, 1898, failed to give a positive reaction. Investigations conducted by Ross, work ing in Calcutta, proving that the "dap pled-w inged" or gray mosquito is the only one concerned in the infection of birds with the Proteosoma coccidia, as well as the demonstration by Bignami, Bastianelli, and Grassi of the develop ment of crescents in the middle intestine of a particular species of mosquito (An opheles clariger), forced Bignami to the conclusion that these inoculation-experi ments failed because tbe proper variety of mosquito was not employed. Follow ing the publication of an article by Grassi in September, 1898, establishirig the fact that certain species of mos quitoes were found in malarious districts which did not exist in healthy regions, Bignaini repeated his experiments with mosquitoes obtained from highly-rnalari ous districts. It is needless to mention that every assurance was had that the patients, the subjects of experimentation, had never been subjected to the possi bility of malarial infection. The mos quitoes used in the first and unsuccessful experiments were foun'd by Grassi to be. long to the Culcx pipievs, while those from which successful inoculations were obtained were identified as the Cular prnicillaris, Citlex malarim (so called), and Anopheles claviger, these latter species being those found by Grassi in malarious regions, the Unica. pipiens be ing the predominating species in regions non-malarious.
Bignami's experiment was begun on September 26, '98, and on November 1st following the patient was seized with a severe chill. The subsequent symptoms were those characteristic of an restivo autumnal infection and the success of the experiment as fully demonstrated by finding in the blood the cestivo-autumnal parasite. tlAmEs C. WiLsoN and THOMAS G. ASHTON.] At the present time there are only two theories as to the mode of transmission of malarial infection which are worthy of consideration,—namely, that it occurs aMally or else by inoculation through the agency of suctorial insects. Welch (Johns Hopkins Hosp. Bull., Mar., '97).
Mosquitoes not considered as essential for the conveyance of the parasites; they are not numerous in the fever-stricken districts on the West Coast; only appear for a short period in the year. Surg Capt. Duggan (Lancet, Mar. 27, '97).
While mosquitoes are almost confined to tropical and subtropical regions, ma laria has a much wider area of incidence. A mosquito- and a malaria- map would be by no means correspondent in area, the former covering a much smaller tract of country than the latter. In seasonal charts, too, the occurrence of malaria would be, with spring and autumn rises, continuous; that of mosquitoes, or their representatives in temperate regions, would be intermittent. William Sykes
(Brit. Med. Jour., Jan. 1, '98).
Transinission of malaria is by the mos quito. Infection occurs chiefly at night. Where there are no mosquitoes, there is no malaria. Thus there is a small island in Cerman East Africa which is free of mosquitoes, and is also free of malaria. The Usamba region, at a. certain height, is also free of malaria. It is also free of mosquitoes. R. Koch (Deutsche med. Woch., June IS, '93).
The malarial parasite cannot be de pendent upon man for its existence, be cause it is sometimes present in regions that were previously uninhabited. This cannot bc explained by simply stating that the plasmodium lives and multiplies in the soil, and that inan is merely an accidental host, for it would then be diffi cult to see how such a soil-parasite could adapt itself so perfectly to an animal organism, such as that of Man ; and it • .... I. a siine..1 that a mosquito or it 1.• I a% 1%1 !IS OW 110,a, for the in If 1.1. II 01 oin• rativnt into • ti t I It t I I 110( Siltlit't. 10 Start 7.111 cpb t fe.‘er unless the suitable --• t. is it band to carry the disease t %iidte%% Dal idson (EdinbUrgh N't ' , t , • 1 1.-alarial parasite possesses an 1.al nhich is completed thy stomach-mall of mosquitoes of the us anoph.lcs. Members of the genus s. ian transmit malaria front in f t,i1 to non infected individuals.
kt th. pr. sent moment this is the only thod by which malaria may be inir. Thi, theory explains most .. 11 litions associated with malarial in f. t titql reports showing the protective tditacy of mosquito-nets even in the ost malarial districts are rapidly ac iumulating; there is no serious evidence in supf ort of any other theory.
lhe evidence at present possessed tends to favor the theory that the tnosquito (an aiquire the infectious agent only from man. The statement is often made, that in tropic-al Africa, for instance, ex loring parties may spend considerable periods of time in the uninhabited in terior mithout illness, even though the regions may appear, from outward con litb_ns, most unhealthy. It is only on their return to the sea-coast to districts lure the surroundings would appear to 1•• better, that the outbreaks of malaria eeur. This hitherto inexplicable fact lee. it.es clear if one assumes that in the «ds, though all conditions are present r a spread of the disease, the mos q litres are unaffected, and, therefore, •rn '.•-: it is only on coming hack to toe settluitent where infected mosquitoes ur that the disease breaks out.
•-tudics by Celli and Delpino, by Grassi, 1 y Ifastianelli and l'4mami, of epidemics in small eommunities, have shown that the vernal cases of malaria are almost r r sf -; that during the month of .1.4ne the anopheles begin to be active: t -It about a month after the beginning f the activity of the anopheles the true ei idemie of malaria begins, starting ap r .rently in foci about individuals who bare recently suffered from relapses of the disease. During the season in n anopheles prevail the malarial epidemic flourishes, ony to disappear again with the disappearance of the mosquitoes. W. S. Thayer (Phila. Mcd. Jour., :May 5, 1900).