. Smithsonian miscellaneous collections. empt to feed, with theresult that the oesophagus is filled to repletion with still more tension thus created produces a regurgitation with each newattempt at feeding, and the contaminated blood of the oesophagus isthus injected into the puncture. All rodent fleas are not susceptible in the same degree to blockageof the stomach, and hence different species are not equally dangerousas spreaders of plague. The highest incidence of transmitted infectionobtained experimentally is always with the Old World rat flea,Xenopsylla cheopis (Roths.). This
. Smithsonian miscellaneous collections. empt to feed, with theresult that the oesophagus is filled to repletion with still more tension thus created produces a regurgitation with each newattempt at feeding, and the contaminated blood of the oesophagus isthus injected into the puncture. All rodent fleas are not susceptible in the same degree to blockageof the stomach, and hence different species are not equally dangerousas spreaders of plague. The highest incidence of transmitted infectionobtained experimentally is always with the Old World rat flea,Xenopsylla cheopis (Roths.). This species is now widely distributed, NO. BITING AND SUCKING INSECTS SNODGRASS 91 particularly in warmer regions; it occurs in most of the coastalports of the United States, and has been found in a number ofinland States where formerly the climate was supposed to be toosevere for it (see Ewing and Fox, 1943). Plague is probably endemic in many localities among wild rodents,but human infection from such sources is rare. In a study of plague. Fig. 35.—The alimentary canal of a flea, and its stoppage with plague bacteria.(A-C, from Faasch, 1935; D, E, from Bacot and Martin, 1914.) A, outline of a flea and the alimentary canal, left side. B, section of pro-ventriculus and anterior end of ventriculus, showing proventricular spines andstomodaeal valve. C, spines of proventriculus, with plague bacteria, Pastcurellapcstis, lodged among them. D, lengthwise section of oesophagus, proventriculusand anterior end of ventriculus from a rat flea, Nosopsyllus jasciatus (Bosc),with stomach entrance blocked by a plug of plague bacteria. E, a flea havingthe proventriculus and stomach entirely filled with mass of plague bacteria. AInt, anterior intestine; An, anus; b, blood in oesophagus; Mai, Malpighiantubules; Oe, oesophagus ; Pp, mass of Pastcurella pcstis in proventriculus ; Prvnt,proventriculus; Rect, rectum; rp, rectal papillae; s, proventricular spines;SVlv, stomodaeal valve; Vent, ventricul
Size: 2067px × 1209px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
