The Hæmosporidia.—It is likely that this order (see p. [151]) may be soon abolished. Mesnil[1270] (April, 1915) considers that the grouping of the three families, Plasmodiidæ (or Hæmamœbidæ), Hæmogregarinidæ and Piroplasmidæ in the order Hæmosporidia is no longer possible, because of the coccidian nature of the Hæmogregarines (see p. [154]). The Coccidia are divisible into the Adeleidea and the Eimeridea (see p. [141]). The Hæmogregarinidæ are allied to the former, and the Plasmodiidæ to the latter. The Piroplasmidæ, until more is known of their life-cycle in the invertebrate host, cannot be more definitely placed.
The Leucocytozoa of Birds.—Regarding the statement, on p. [153], that Laveran and França consider that avian leucocytozoa may inhabit red blood cells, it may be added that França[1271] (April, 1915) remarks that the action of the parasites on the red cells is very rapid and very intense. The host cells become so altered that it is difficult to recognize their true nature. He used very young birds in his researches. Two shapes of host cell are considered, namely, those with fusiform prolongations, and those which are rounded and without such prolongations (see p. [153]). The movements and form of the Leucocytozoa determine the shape of the host cell, as was pointed out by Fantham[1272] in 1910.
Schizogony of these parasites has been seen by França (1915) and by Coles (1914), in addition to Fantham (1910), and to Moldovan (1913), mentioned on p. [153]. Schizogony may also take place in the lungs of the host. The genus Leucocytozoön, established by Ziemann in 1898, belongs to the family Hæmamœbidæ.
II.—FORMULÆ OF SOME CULTURE MEDIA.
(1) Culture Media for growing Amœbæ.—There has been much discussion as to whether the true parasitic Entamœbæ or Endamœbæ can be grown on culture media (see p. [42]). Undoubtedly certain free-living amœbæ can be so grown, and it is considered that some of the earlier researches on the so-called artificial growth of the dysenteric amœbæ were really due to contaminations with free-living forms. The following media are worthy of note:—
Musgrave and Clegg in 1904 devised a culture medium for amœbæ. The organisms grown by them were probably not dysenteric amœbæ, as was thought, but free-living forms. Phillips[1273] (1915) gives a slightly modified formula of Musgrave and Clegg’s medium, thus:—
| Agar-agar | 2· | 5 | grm. |
| Sodium chloride | 0· | 05 | " |
| Liebig’s beef extract | 0· | 05 | " |
| Normal sodium hydroxide | 2· | 0 | c.c. |
| Distilled water | 100· | 0 | " |
Without clarifying, sterilize at 7 kilograms pressure per square centimetre for about three-quarters of an hour. It should be neutral to phenolphthalein.
Anna W. Williams[1274] (1911) described a medium consisting of fresh tissue spread on agar plates for the culture of amœbæ. There are three stages in the procedure: (1) obtaining living amœbæ free from other living organisms; (2) obtaining sterile tissue; and (3) making successive transplants of amœbæ and tissue, and showing that every transplant is free from other living organisms. Each step requires many controls. The essentials of the method may now be given. Remove aseptically and rapidly the tissue required, such as brain, liver, kidney, or spleen, from a freshly killed animal (guinea-pig, rabbit, or dog). Put each tissue on a separate agar plate. Cut the selected tissue into tiny pieces, and spread them over freshly made agar plates. Place these plates in a thermostat at 36° C. for twenty-four hours to insure sterility. Add the broken up tissue to the amœbæ, free from bacteria, and maintain the cultures in thermostats, some at 36° C., and some at 20° C. to 24° C. Emulsions of liver and brain in sterile neutral glycerine may also be used. The freshly removed tissue serves as food for the amœbæ.