gates in the lumen of the alimentary tract and passes out with the feces. This is the supposed means of transmission between lice. The original lice were taken from horses, but the latter are not presumed hosts of the organism as the lice do not suck the blood of their hosts. 6. Wolbachia linognathi (Hindle, 1921) Philip, 1956. (Rickettsm linognathi Hindle, Parasitology, 13, 1921, 157; Philip, Canad. Jour. Microbiol., 2, 1956, 267.) li.nog.na'thi. M.L. noun Linognafhus a genus of sucking lice; M.L. gen. noun linognathi of Linognathus. Resembles Wolbachia trichodectae in ap- pearance. Stain bluish with Giemsa's stain. Cultivation: Not reported. Source: Observed in two of 57 goat lice {Linognathus stenopsis), where it was found extracellularly in the lumen of the gut. Probably not pathogenic for the host, but also not adapted to the point of occurring in a high percentage of neighboring hosts. 7. Wolbachia melophagi (Noller, 1917) Philip, 1956. (Rickettsia melophagi Noller, Arch. f. Schiffs- u. Tropen-Hyg., 21, 1917, 70; Philip, Canad. Jour. Microbiol., 2, 1956, 267.) me.lo'pha.gi. M.L. mas.n. Melophagus a genus of sheep keds (sometimes incorrectly called "ticks"); M.L. gen. noun melophagi of Melophagus. Minute, rickettsia-like, extracellular, coc- coid, ellipsoidal and, occasionaly, short rods occurring characteristically in pairs of fairly uniform size, 0.3 to 0.6 micron in diameter. In eggs of the wingless-fly host, the organisms are more rod-shaped with a tendency to pleomorphism. In cultures, the rods may measure up to 1.0 micron in length. Stain purple with Giemsa's stain and reddish with Macchiavello's stain. Gram-negative. Cultivation: This is the only one of the rickettsia-like microorganisms that has been confirmed as cultivable on non-living media (glucose-blood-bouillon-agar). Also grows in embryonated chicken eggs. Pathogenicity and source: Occurs as con- tinuous or broken masses lining the intesti- nal epithelium; occurs extracellularly in the sheep ked ("sheep tick") (Melophagus ovinus). Intracellular growth has been disputed and is not generally credited at present. Injury to the host has not been re- ported, and since this organism is almost universally present, including the larvae of the viviparous host, s3^mbiosis is an ad- vanced stage approaching the condition in Syinbiotes lectularius without the develop- ment of mycetomes. Infection in ked-in- fested sheep is disputed, and cultivation from sheep's blood has been claimed. At least such an infection is low-grade or in- apparent as far as symptoms are concerned. Laboratory animals, including vitamin-de- ficient guinea pigs, have failed to become infected by injection of cultures. 8. Wolbachia dermacentrophila (Stein- haus, 1942) Philip, 1956. (Rickettsia derma- centrophila Steinhaus, U. S. Public Health Rept., 57, 1942, 1376; Philip, Canad. Jour. Microbiol., 2, 1956, 267.) der.ma.cen.tro'phi.la. M.L. noun Derma- censor a genus of ticks; Gr. adj. philus loving; M.L. adj. dermacentrophilus Derma- centor -omg. Minute, rickettsia-like organisms, meas- uring 0.3 to 0.8 by 0.5 to 2.8 microns. May occur joined in short chains of two or three organisms or occasionally as filaments. On the average, larger in size than Rickettsia rickettsii. Stain reddish with Machiavello's stain and bluish with Giemsa's stain. Not acid-fast. Gram-negative. Cultivation : Failed to grow on 14 ordinary cell-free, bacteriological media. Readily cultivated in embryonated chicken eggs, growing chiefly in yolk sacs and apparently in the embryonic fluids. Pathogenicity and source: Found most abundantly in the epithelial cells of the intestinal diverticula of the Rocky Moun- tain wood tick (Dermacentor andersoni) , but may also occur throughout the various tis- sues of the host. Extracellular occurrence is also possible. Observed in every stage of the tick host including the egg. Not lethal for the tick host. Attempts at infecting various laboratory animals susceptible to spotted fever failed; such animals were not immune to challenge with strains of tick- borne, rickettsial pathogens. Spotted-fever-
