30 which suggested that these parasites had affinities with the flagellata, and by
those of Koch and Kliene, who described certain very peculiar developmental ...
30
which suggested that these parasites had affinities with the flagellata, and by those of Koch and Kliene, who described certain very peculiar developmental forms in the tick. In tracing a protozoon parasite through its intermediary host there are in practice many difficulties which I need not refer to here, and those in connection with piroplasma were especially great on account of the small size of the parasite and the fact that the examination of the tick is more difficult than that of other insects. Before taking up the research it was found necessary to make a preliminary study of the anatomy and histology of ticks. Again it was necessary to be certain that the right species of tick was being investigated and since H. leachi, the only species of tick actually known to transmit Piroplasma canis, does not occur in India, the claims of other species had to be considered and their pathogenicity worked out. After months of work it became clear that the species R. sanguinens (Latrine) conveyed the disease, and a minute investigation of ticks fed upon infected dogs was commenced. In spite however of the most laborious examination of the contents of the gut of ticks fed on suitable cases nothing was to be found suggesting development. Work was therefore directed to the question of the existence of sexual forms in the blood and the varieties of the parasite seen at different stages of infection, but without result. Cultures were then undertaken on lines previously adopted with the Leishman- Donovan Body, but as in the hands of other authors nothing definite was obtained ; nor was the examination of preparations kept in the warm chamber, as for demonstrating the flagellation of the malarial parasite, more successful. Koch's and Kliene's researches stimulated me to renewed efforts, which were at first directed to the obtaining of the cultural forms of Kliene, but though some results were obtained they were indefinite and unsatisfactory. Curiously enough development was first seen when I was endeavouring to follow up the cycle of development of the hæmogregarine Leucocytozoon canis in ticks fed on a dog who during the experiments developed a severe attack of piroplasmosis. In a preliminary note in the Indian Medical Journal I described the club shaped bodies of Koch and some other appearances suggesting the conjugation described by this author. A little later in a preliminary note in the British Medical Journal I gave a description of developmental stages leading up to the formation of swarms of sporozoit-like bodies in the salivary glands of the nymph and adult of the second generation. Since then many gaps have been filled and certain errors of interpretation have been corrected, with the result that the cycle of development can be followed concisely and clearly. A complete description of all the forms observed would occupy too much space in this report, but a summary may be given. Parasites not differing from ordinary forms in the peripheral blood, when in the gut of the tick, enlarge and form round or oval bodies 4 µ. to 5µ.indametrwhc oainstlrembhofignal piroplasma of the blood. Before they have reached their full size these bodies often show irregularities, but the long processes described by Koch do not seem a neces-sary part of development. After reaching the size noted an achromatic line appears giving rise to some peculiar appearances wrongly interpreted by me in my first note. This line divides the parasite approximately into two halves, one containing the chromatin mass, and the other no chromatin. The two halves eventually separate except at one point and the portion without chromatin swings round to become the tail of a club shaped body, the half with chromatin forming the anterior portion. The club shaped body at first somewhat irregular in shape takes on, as it becomes more mature, the appearance of a vermicule and develops a peculiar apparatus at the anterior end. The club shaped bodies then sooner or later leave the gut and are found about the ovary and oviducts. It was somewhat of a surprise to find that this development which takes place in the gut of the adult tick also takes place in the gut of nymphs fed on infected dogs. My experiments have not yet proved that infection can be transmitted otherwise than hereditarily, but there can be little doubt from the microscopical
