The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . e or twoflagella and an undulating membrane, and specially adaptedfor Ufe in the blood of a vertebrate. Of late years considerableprogress has taken place in our knowledge of these organisms,research upon them having been stimulated by the realizationof their extreme importance in medical parasitology. Not onlyhas the number of known forms been greatly multiplied, butthe study of the biology and Ufe-history of the parasites hasbeen attended in some cases with remarkable and unexpectedresults. Hist
The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . e or twoflagella and an undulating membrane, and specially adaptedfor Ufe in the blood of a vertebrate. Of late years considerableprogress has taken place in our knowledge of these organisms,research upon them having been stimulated by the realizationof their extreme importance in medical parasitology. Not onlyhas the number of known forms been greatly multiplied, butthe study of the biology and Ufe-history of the parasites hasbeen attended in some cases with remarkable and unexpectedresults. Historical.—The first observation of a trypanosome is usuallyascribed to Valentin (55), who in 1841 announced hus discovery ofcertain amoeboid parasites in the blood of a trout. In the two orthree years following several other observers recorded the occur-rence of similar haematozoa in various fishes. The generic nameof Trypanosoma was conferred by Gruby in 1843 upon the well-known parasite of frogs. E. Ray Lankester (iS) subsequentlydescribed this same form (under the name of Undulina ranarum). A B {From Lankester.) Fig. I.*—Undulina ranarum, Lankester, 1871. In B the nucleusis shown. and was the first to indicate the presence of a nucleus in thecell-body. To Mitrophanow (1883-18S4) and Danilewsky(1885-1889) we owe the first serious attempts to study the com-parative anatomy of these haematozoa. Trypanosomes werefirst met with in cases of disease by Griffith Evans, who in 1880found them in the blood of horses suffering from surra in 1894 (Sir) David Bruce discovered the celebrated SouthAfrican parasite {T. briicci) in cattle and horses laid low withnagana or the tsetse-fly disease; and this worker subsequentlydemonstrated, in a brilliant marmer, the essential part playedby the tsetse-fly in transmitting the parasites. The creditfor first recognizing a trypanosome in human blood, anddescribing it as such, must undoubtedly be assigned toG. Nepveu (189S). Trypanosomes w
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