Diagrams of Chilomastix mesnili are given in fig. 423.
Giardia (Lamblia) intestinalis (see p. [57]).—Alexeieff[1254] (1914) considers that Lamblia intestinalis, Lambl, should be placed in the genus Giardia, Kunstler, 1882. Bipartition occurs in the encysted state. The axostyles persist in the quadrinucleate cyst.
Cercomonas hominis (see p. [61]).—This parasite is considered by some authors to be of a doubtful nature, as it is thought to have been mistaken for deformed or incompletely observed Trichomonas or Chilomastix or even Lamblia.
Wenyon[1255] (1910) described Cercomonas longicauda from cultures of human fæces. It is considered that the genus is very confused, and the author points out that the tail flagellum has been overlooked. He considers that the genus Cercomonas should include flagellates with an anterior blunt end from which arises a single long flagellum, and a posterior tapering end also with a flagellum, which can be traced over the surface of the body towards the insertion of the anterior flagellum.
Another species, Cercomonas parva, has been found in cultures of human fæces by Hartmann and Chagas[1256] (1910). It has a somewhat different structure.
Further researches are necessary on the organisms variously referred to the genus Cercomonas.
Transmissive Phase of Trypanosomes in Vertebrates.—In addition to the general remarks on the morphology of trypanosomes set forth on pp. [70] to 72, it may be noted that Woodcock[1257] (November, 1914) states that, in certain cases, there is a definite transmissive phase of a trypanosome in its vertebrate host. He quotes the work of Minchin and himself on T. noctuæ of the little owl, in which the transmissive form is spindle-shaped and occurs in the bird’s peripheral blood during the early summer months (see p. [69]). A similar phase occurs in T. fringillarum, and Robertson[1258] has found that the short, stumpy form of T. gambiense is its transmissive phase in vertebrates.
Trypanosoma lewisi (see p. [88]).—Brown (1914–15) has published some interesting results on the potential pathogenicity of T. lewisi.
Blepharoplastless Trypanosomes (see p. [101]).—Laveran[1259] (April, 1915) suggested a practical use of strains of blepharoplastless trypanosomes produced by the action of drugs. He finds that tryposafrol will also produce such strains, and remarks on blepharoplastless strains of T. evansi and T. brucei, which in the former case can undergo 450 passages without reversion, and in the latter 273 passages. He states that if it is desired to inoculate surra or nagana to Capridæ or Bovidæ in order to produce immunity, use should be made of the blepharoplastless races of the respective trypanosomes, which races are a little less virulent than the corresponding normal ones. Also, the immunity which follows from an infection due to blepharoplastless T. evansi or T. brucei is only a little less complete than that following infections from either of the respective normal strains.
The Experimental Introduction of certain Insect Flagellates into various Vertebrates, and its bearing on the Evolution of Leishmaniasis.—In continuation of the remarks on pp. [103], 104, and [112], further researches have been conducted on the introduction into vertebrates of flagellates normally parasitic in insects. The vertebrates became infected by inoculation with the flagellates or by being fed on insects containing the protozoa. Fantham and Porter[1260] (June, 1915) published the following results. Flagellates from sanguivorous and non-sanguivorous insects were used, and cold-blooded as well as warm-blooded vertebrates as hosts. The introduced protozoa were pathogenic to the mammals, but not markedly so to the cold-blooded vertebrates. Herpetomonas jaculum, H. stratiomyiæ, H. pediculi, and Crithidia gerridis (parasitic in certain waterbugs) proved pathogenic to mice. A puppy was infected by way of the digestive tract with H. ctenocephali. Frogs became infected with H. jaculum and with C. gerridis, toads and grass snakes with H. jaculum, lizards with C. gerridis, and sticklebacks with H. jaculum. Second and third passages of some of the parasites were obtained. The protozoa, whether Herpetomonas or Crithidia, were present in the vertebrate hosts in either the non-flagellate or the flagellate form, or usually both. They were more abundant in the internal organs of the hosts, more particularly in the liver, spleen and bone-marrow. In all experiments in which C. gerridis was used the parasite invariably retained the crithidial facies in the vertebrate host. No transition to a trypanosome was ever seen. Infections in adult animals were not so heavy as in the young ones, and the parasites were more virulent in young hosts, as is the case with Mediterranean kala-azar in children.