It is now twelve years since it first became possible to study plague by modern methods, and yet no conclusion on its aetiology has been reached which has met with general acceptance. Two causes, as it seems to me, have chiefly contributed to this disappoinment. One consists in the appeal which has been persistently made to bacteriology for the lights which in fact are not in its power to shed; the other is neglect of the epidemiological method, or at least failure to apply it effectively. In consequence, a field has been occupied by the bacteriologist which could not be profitably laboured by him. The epidemiologist has not seriously disputed this usurpation of his domain, and for his apparent apathy he has not been without excuses of some weight.

The cases which from the subject of the following note occurred in the district of Dr Chas. Jackson, M.O.H., of Fulham, and I am greatly indebted to him for so kindly furnishing me with their histories and with samples of the patients' serum.

The material on which these notes are founded was obtained from moles captured in the neighbourhood of the Lister Institute at Elstree in Hertfordshire from the middle of May to the beginning of July, 1906. In all 14 moles were examined.

While studying the infection of Trypanosoma dimorphon in mice at the Pasteur Institute some five months ago, I noticed in one of the fresh blood preparations made from a brown mouse (A) infected with the trypanosomes, a small and very active spirochaete. At first I was of the opinion that its presence in the blood was due to contamination from the skin, but, as it was constantly present and was constantly present and was found in blood taken from any part of the body, it was evident that it was parasitic in the blood.

In the present paper we describe the results of further investigations on the morphology and staining characters of Piroplasma canis, as well as a large number of observations on the living parasites. Our previous papers (1905) contained the results of studies preliminary to the investigation of the life-history of the parasite, but further work was unavoidably interrupted owing to the difficulties attending this form of research—we unaccountably failed to transmit the disease after several passages through dogs, and met with great difficulties in rearing progeny from infected ticks. Consequently the observations had to be discontinued until, after several failures, infected ticks (Haemaphysalis leachi) capable of transmitting the disease, had been received from South Africa through the kindness of Mr C. P. Lounsbury, Government Entomologist, Cape Colony. With this fresh strain of the disease we have succeeded in demonstrating various points in the morphology of the parasite which have hitherto escaped observation, and have worked out its method of multiplication in the living blood. Further studies have also been made on the vitality of the parasite outside the body in culture fluids, but these and other studies on the cycle of development within the tick are reserved for future communications.

In the light of the controversy which is beginning to be waged in connection with Schaudinn's researches into the life-history of Halteridium noctuae, and especially in view of the papers by Prof. Ross which have been appearing in this Journal, the accompanying illustrations are likely to be of interest. They represent forms of parasite which I have found in the alimentary tract of the flea, Pulex cleopatrae Roths. and possibly other species, when searching for a cycle of development for Haemogregarina balfouri Laveran in that insect which, along with mites, infests the Sudan jerboa (Jaculus gordoni). The illustrations were prepared by Mr Richard Muir from drawings which I made in Khartoum.

Many investigations relating to Hygiene and Public Health, possessing permanent scientific value, appear in Annual Reports of Medical Officers of Health, Blue Books and other Publications of Official Bodies within the British Empire. These are not easily available and as a rule no record of them, appears in scientific journals or in an accessible form; consequently much valuable work is lost sight of. To obviate this difficulty the Editors of the “Journal of Hygiene” propose to publish from time to time abstracts of such publications, or parts of them, as appear of sufficient permanent interest. They will be glad to receive copies of official Reports coming under the above description.