Pasteur, in May 1884, showed that if the rabies virus of the dog was passed from rabbit to rabbit, or guinea-pig to guinea-pig, it gradually became exalted in virulence and fixed in incubation period for these rodents. This fixed virus remained exalted in virulence when inoculated subdurally into other animals. Magendie held the opinion that the rabies virus, when transmitted by bites from dog to dog, lost its virulence by about the fifth passage.

During the past three years I have made various attempts to raise Dermacentor variabilis through its various stages on tame rabbits and have at last been successful. Though there are still many points connected with the life-history to clear up, it is at any rate the first step towards finding ways and means for its control.

During August and September 1909 I had an opportunity, thanks to the Government Grant Committee of the Royal Society, of making a fairly comprehensive examination of the parasites of fishes from the English Channel at the Marine Biological Laboratory, Plymouth. During that time nearly five hundred fishes, belonging to about 80 species, were dealt with and a very extensive collection of parasites made. A considerable number of species were obtained many of which are new to British waters but the number of absolutely new species amounted to very few. Of these I am describing here four of the most noteworthy, three of which appear to be of new generic type. A complete account of the investigations will be published later.

History. Trypanosomes have been cultured from the blood of cattle in many parts of the world; in Germany, Denmark, Greece, Holland, France, Russia, Japan, the Philippines, Siberia, Algeria, Tunis, the United States and Brazil. But in only a few cases have the actual parasites been found in the circulating blood. From the scanty literature at my disposal, but especially from the Sleeping Sickness Bulletin, I find that the following observers have found and described the trypanosomes in the blood.

Under the term “Spirochaetosis” are included those diseases of man and animals due to the spiral microorganisms known as spirochaetes. I shall confine myself to those which produce blood infection—the relapsing fevers—in which a remarkable periodic increase and decrease in the number of the spirochaetes is observable corresponding to alternating rises and falls of the host's body-temperature. Authority is divided as to whether the spirochaetes are Protozoa or Bacteria, and the matter is a fruitful theme of discussion upon which I shall not enter here. Judged, however, from their pathological effects and their prompt reactions to immune sera and certain drugs, they show a pronounced affinity to Protozoa and exhibit phenomena not hitherto observed in Bacteria.

The term trypanosomiasis is applied to-day to a group of diseases affecting vertebrates and caused by parasitic Protozoa belonging to the family Trypanosomidae. These parasites occur chiefly in the blood plasma and the typical form possesses an elongated body, an undulating membrane, a single nucleus, a blepharoplast, and a chromatic filament running along its length from near the blepharoplast, along the margin of the undulating membrane, to terminate freely at one end of the body. The latter has a somewhat spiral form, the protoplasm being alveolar and at times showing a granular structure. An axial filament has been described as occurring in some forms. One species, Trypanosoma equiperdum, occurs largely in the lymph, and another, T. gambiense, may invade the cerebrospinal fluid. They are actively motile organisms, multiplying usually by longitudinal or multiple division. Numerous species of trypanosomes have been successfully cultivated in vitro in the presence of haemoglobin, and by this means many trypanosomes have been discovered in animals in which these parasites occur in such scanty numbers that their presence cannot be detected microscopically. Thus, a large percentage of birds and cattle in different parts of the world have been found to harbour trypanosomes in their blood.

Im Jahre 1908 haben wir auf dem IX. Internationalen Tierärztlichen Kongresse im Haag einen Bericht über die Piroplasmose der Pferde und Esel in Transkaukasien erstattet und etwas später eine kurze Bemerkung darüber in russischer Sprache publiziert. Nachher haben wir aber noch einige Fälle von Piroplasmose bei den Pferden beobachtet, wobei wir die Ansicht Nuttall's bestätigen konnten über die Existenz zweier selbstständiger Arten der Pferdepiroplasmose, welche durch zwei besondere Arten von Blutparasiten der Gattung Nuttallia und Piroplasma verursacht werden.