Neither marked anemia nor anj^ mortality occurs in heavil}' infected animals. Splenec- tomized dogs, white rats and deer mice are not susceptible. Source and habitat: Occurs in the blood of the vole (Microtus pennsylvanicus penn- sylvanicus). The natural mode of transmis- sion has not been determined, though ticks and mites are suspected. 3. Ilaemobartonella lyzzeri (Weinman and Pinkerton, 1938) Weinman, 1944. (Bartonella iyzzeri Weinman and Pinkerton, Ann. Trop. Med., 32, 1938, 217; Weinman, Trans. Amer. Philosoph. Soc, 33 (N.S.), 1944, 314.) tyz'ze.ri. M.L. gen. noun iyzzeri of Tyzzer; named for Dr. E. E. Tyzzer, protistologist and investigator of this group of microor- ganisms. Single or composite rods measuring about 0.25 by 1.4 to 4.0 microns. Short rods averag- ing 0.2 to 0.3 by 0.8 micron as well as round forms with diameters of 0.2 to 0.3 micron also occur. Occasional granular swellings and enlarged poles occur. Stain intensely red-violet with Giemsa's or with May- Griinwald-Giemsa's solutions. Gram-nega- tive. Cultivation: Initial cultures on Noguchi's semi-solid serum agar are obtained irregu- larlj When incubated at 28°C., colonies appear as isolated, white spheres about 1 mm in diameter in the upper 8-mm border of the medium. The clumps are composed of rods and granules with larger round structures or discs occurring occasionally. Also cultivated on the Zinsser, Wei and Fitzpatrick modification of the Maitland medium. Prolonged maintenance on semi- solid media has not been obtained. Pathogenicity: Splenectomized, haemo- bartonella-free guinea pigs may be infected by blood or by cultures injected subcutane- ously or intraperitoneally. Splenectomized, Haemobartonella muris-free rats are not sus- ceptible when inoculated with infected guinea-pig blood. Monkeys (Macacus rhesus) are also not susceptible to inoculations of infected blood, tissue and cultures. Infec- tion of the guinea pig is subclinical in its manifestations. No definite anemia accompanies infection. Comment: Since 1944, at which time this species was classified as belonging to the genus Haemobartonella, knowledge has accrued which suggests a restudy to deter- mine whether this species might more properly be placed in the genus Grahamella. Source and habitat: Found in the blood of the Peruvian guinea pig (Cavia porcellvs) ; also encountered in the blood of native guinea pigs in Colombia. Observed in la- tently infected animals only after splenec- tomy. The natural mode of transmission is unknown, although the flea may be a possi- ble vector. 4. Haemobartonella peronij sci Tyzzer, 1942. (Proc. Amer. Philosoph. Soc, 85, 1942, 377.) pe.ro. mys'ci. M.L. mas.n. Peromyscus a genus of mice; M. L. gen. noun peromysci of Peromyscus. Occurs as delicate, filamentous forms (which may be branched) on red blood cells. These filaments may become beaded and may give rise to a number of coccoids and rods from which ring forms may develop. Stains by Giemsa's method, but the staining process must be intense in order to demon- strate the organism. Pathogenicity: Infection transmissible to splenectomized white rats (irregularly), white mice (frequently) and voles, produc- ing a more or less severe illness with anemia. Habitat: Found in the blood of deer mice (Peromyscus leucopus novaboracensis) . 5. Haemobartonella sciiiri Tyzzer, 1942. (Proc. Amer. Philosoph. Soc, 85, 1942, 385.) sci.u'ri. M.L. mas.n. Sciurus a genus of squirrels; M.L. gen. noun sciuri of Sciurus. Very polymorphic Occurs as minute rods and filaments which are either continuous or segmented. The rods and filaments vary in thickness, some being very uneven and some very coarse. Beaded chains may de- velop from the thickened forms. The bead- like elements stain a dull reddish at the periphery with Giemsa's stain, while the remainder is very faintly stained in con- trast to the intensely staining basophilic rods and filaments. Some of the rounded forms have the appearance of large, thick
