1. Progressive anaemia was observed in 30 White Leghorn hens obtained from a poultry farm in England, where the ailment became noticeable through the yellowish-paleness of the combs and gills of the diseased hens and the heavy mortality following on the appearance of these symptoms.

Only hens of one stock were affected, other breeds on the same farm did not develop the same or a similar condition.

2. The anaemia was characterised by a lasting diminution in the normal number of erythrocytes, a Hb index less than 1, the preponderance of immature and deformed erythrocytes and the presence of marrow-cells of the erythrocyte series in the circulating blood. The leucocytes were normal or slightly below normal in numbers; the monocytes were diminished.

3. The essential pathological lesion is an intravascular proliferation in the marrow of the stem cell of erythrocytes, which results in the blood-stream being overrun with erythroblasts and immature erythrocytes; these are rapidly destroyed in the spleen and liver, whilst the issue of normal erythrocytes in the marrow is hindered. The myeloblastic elements do not proliferate actively. These lesions explain the pathogenesis of the anaemia.

4. This intensified activity of the bone-marrow, the resulting congestion and increased localised pressure, induce the production of osteoid tissue; the femur and other bones of the fowls thicken, so that the medullary canal is nearly obliterated.

5. Attempts to detect microbes in the blood or isolate bacteria from the organs of anaemic hens failed. The spontaneously diseased hens all harbour a minute cestode, Davainea proglottina, in the duodenum, where the helminth causes round-celled infiltration, petechiae and thickening of the intestinal peritoneum.

6. In Davainea-free fowls of the same and other breeds, the injection of blood and cellular emulsions of liver and spleen from erythromyelotic fowls caused a condition of hypercythaemia which lasted several months. This was related to congestion and hyperplasia of the red-blood-marrow and accompanied by considerable enlargement of the liver and spleen.

7. Typical erythromyelosis was reproduced in one hen of the same stock from the same farm, by the intravenous inoculation of blood and tissue from spontaneously diseased fowls. In other hens only a transient type of anaemia was obtained, corresponding to the experience of other observers, more particularly Bedson and Knight (1924).

The experimental results agree with the view that a proliferative micro-plasm is the specific cause of this condition.

8. It is suggested that the development of this outbreak is induced by the massive infestation of the duodenum with Davainea proglottina. This irritative cestode produces a receptive condition in the bone-marrow of the fowl, which allows the microplasm to unfold its pathogenic properties. The duodenal parasite therefore plays the part of a preparatory cause. The association of cestode and microplasm affords an example of a “compound” disease.

9. The microplasm is specific and multiplying solely in certain definite blood-marrow cells of Gallus domesticus. This proliferative action can be compared to that of the microbes of epitheliosis contagiosa and Rous fowl-sarcoma; the resulting cell-reaction is then similar to tumour formation in these and other tissues of the fowl.

10. Since this haemopathy in fowls is characterised by specific pathological features in the erythrocyte-producing cells of the marrow, the name erythromyelosis is suggested, to mark clearly the position of the principal cellular lesion.

11. This disease (erythromyelosis) has been distinguished from other ailments of fowls, in the course of which anaemia may also occur, e.g. avian tuberculosis with involvement of the marrow. The leucocythaemic type is differentiated by diagnosis of the predominant type of cell found in active multiplication in the blood and the position of the cell-proliferation in the marrow.

12. Bone-marrow tumours and neoplasms of the lymphatic system occur in fowls, without causing progressive alterations in the cellular contents of the blood. The perivascular aggregations of cells in different organs may also hypertrophy, without any cytological changes being noticeable in the blood, except diminution of the numbers of erythrocytes. Such lesions are therefore distinguishable from different forms of leucocythaemia, where a persistent and progressive increase of genetically related cells is noticeable in the bloodstream and is concurrent with certain diffuse lesions of the marrow.

13. The haemoblastic diseases of fowls, such as erythromyelosis, leueo-cythaemia, lymphocythaemia, differ from tumours of the blood-producing tissues, since the former are the result of a pathological disturbance of the mechanism of haemocytopoiesis, whilst the latter are the localised proliferations of cellular elements, which then may spread by a process identical to neoplastic metastasis. There is a distinction in mode and degree.

14. The many resemblances between erythromyelosis and certain blood diseases in man and animals may indicate that their pathogenesis. though not identical, is comparable. A similar analogy may be applicable to fowl-leuco-cythaemia and lymphocythaemia.

1. A study has been made of the effect of acriflavine upon Bodo caudatus. The drug has the property of producing a percentage of modified Bodos without parabasal bodies but no permanently aparabasal strains have been produced.

2. A technique was devised whereby the resistance, as judged by two different types of survival experiment, could be correlated with the percentage of modified Bodos produced when the strain is put to grow in an ascending series of concentrations of acriflavine incorporated in the culture medium.

3. The peak of the count of altered Bodos in relation to the concentration in which it occurs is found to be the index of the sensitiveness of the strain at that date. The maximum reaction as gauged by the numbers of modified Bodos produced in an untreated strain of average sensitiveness is about 70 to 80 per cent., and this occurs in so low a concentration as 1/1,000,000. 1/5,000,000 gives a count below the maximum and 1/50,000,000 produces only 1 to 4 per cent. according to the sensitiveness of the strain.

4. The mass untreated strain was originally derived from a single Bodo isolated in the autumn of 1926. This strain in 1927–28 was used as the mass untreated strain in the experiments. Its resistance was found to fluctuate from below a capacity to evolve with great difficulty in 1/50,000 to a somewhat feeble development in 1/10,000 acriflavine incorporated plates. The mass untreated strain was never able to evolve in plates containing 1/5000 acriflavine at any time.

5. Strains grown from single isolations from the untreated mass culture showed different degrees of natural resistance. The most resistant clones could develop in 1/5000 acriflavine incorporated plates, but not in 1/2000. The great importance of this natural range of resistance in estimating an acquired drug fastness is emphasized. Strains which had been made resistant could be brought to live continuously in 1/1500 acriflavine incorporated plates, but no evolution was obtained in 1/1000.

6. Evidence that drug fastness in Bodo caudatus is due to the interaction of selective inheritance and the actual modification of the quality of the Bodo by evolution in the drug is given. The modification is not apparently a mutation, it is a heritable piling up of changes in a particular direction.

7. A high resistance once acquired is retained through prolonged cultivation upon drug-free media. A gradual loss occurs, partly by a dilution through multiplication of the character impressed and partly by the survival of variants of less resistance to acriflavine, but of perfect viability in other circumstances and the competition of these within the strain. The loss of resistance is greatly accelerated in single cell cultures (clones) isolated from the resistant strains, but up to the present no treated strain has entirely lost the effect of the original exposures to the drug. The longest time elapsing between the creating of a partially resistant strain and its test for resistance above that of the untreated culture is one year.

8. The bearing of the data obtained in Bodo caudatus upon the condition found in trypanosomiasis and upon certain aspects of chemotherapy in this group is discussed.

9. Bodo caudatus being an organism without conjugation and therefore without bi-parental inheritance and consequently lacking the reorganising effect that such a periodic closing of the cycle produces, affords an example of a labile organism capable of being progressively altered within certain limits under the influence of the environment.

The structure of the head and mouth parts of the Streblidae has been very briefly described by Speiser (1900) and subsequently by Muir (1912) in the genera Ascodipteron and Nycteribosca. The description given by the latter author is, however, still incomplete. Having, therefore, collected the necessary material I have re-investigated their structure and compared it with that of the Hippoboscidae and the Nycteribiidae, already described by me elsewhere (1926 and 1928).

Five tame monkeys (3 Macacus sinicus and 2 M. rhesus) have been treated with emetine bismuthous iodide per os, in order to study the effects of the alkaloid upon their intestinal amoebae (and other protozoa).

These monkeys were originally infected with Entamoeba histolytica (large and small strains), Entamoeba coli, Endolimax nana, Enteromonas (= Tricercomonas), and Giardia. Treatment with emetine ultimately eradicated the E. histolytica infections from four out of five animals, but did not remove any of their other intestinal protozoa.

It has been found necessary to administer 60 mg. of emetine bismuthous iodide daily for about a week to a macaque weighing about 5 kg. in order to eradicate an infection with E. histolytica. Such dosage was toxic to four of the five monkeys used.

The general conclusion drawn is that emetine affects the various intestinal protozoa of M. sinicus and M. rhesus exactly as it does the comparable species in man; and it is suggested that macaques can therefore be utilized—if similar methods be employed—in place of men in future chemotherapeutic experiments directed towards the discovery of remedies for human amoebic dysentery.

From the small intestine of a lynx, Lynx canadensis, killed in the vicinity of Minneapolis, Minnesota, four strobilae and two fragments of an undescribed taenioid cestode were recovered. The largest of these tapeworms, which is the only one containing segments in all stages of development, measures 31 cm. in length and contains 253 proglottids; the other three strobilae measure 8, 26 and 30 mm. in length, respectively. The two fragments, one consisting of three and the other of eight ripe proglottids, apparently are segments from the largest one of these four strobilae.

In 1926 Bequaert wrote, “In the light of the theory of evolution, the various cases in which hemipterous insects, that are normally predaceous or even phytophagous, occasionally become blood-suckers are of considerable interest. They show that haematophagous habits may be readily and rather suddenly acquired by insects that have developed suitable piercing and sucking mouth-parts, without previous adaptation to a blood diet.” These remarks accompanied an annotated list of the species of Hemiptera known to bite man without provocation. In the list are included six species of Cimicids and eleven Reduviids (Triatoma and Rhodnius) which are apparently obligate blood-suckers of Vertebrates; and nine Reduviids, one Nabid, five Anthocorids, and two Lygaeids (Geocoris henoni Puton and G. scutellaris Puton) which are normally predaceous on other insects, whose haemolymph they suck, being thus obligate blood-suckers of Arthropoda. The case of Clerada apicicornis Sign. is obscure, though this species is probably normally predaceous on other insects. An Australian species (C. nidicola Bergr.) is an inquiline in the nests of “opossums” (phalangers).

1. Two pure strains of Entamoeba coli, differing in their accompanying bacterial flora and experimental history, but identical morphologically, have been tested with emetine hydrochloride in vitro.

2. In a buffered and wholly liquid medium, with a pH varying between 6·8 and 7·2, emetine hydrochloride was found to be toxic to E. coli in dilutions between 1 : 300,000 and 1 : 600,000, the toxicity increasing with the alkalinity of the medium.

3. It is therefore concluded that emetine is about 16 times as toxic in vitro to E. histolytica as it is to E. coli.

While working on parasites of fish for the New York State Conservation Department during the summer of 1928 it was possible to secure experimental evidence on the life-cycle of Proteocephalus pinguis La Rue 1911. The adult parasite lives in the digestive tract of Esox lucius Linnaeus and E. reticulatus Le Sueur where it ranges in length between 50 and 90 mm. Since La Rue (1914) gives a complete description of the adult it is not necessary to go further into the morphology of this form. Adult tapeworms for the experiments were taken from E. lucius from Lake Erie and Ellicott Creek, near Buffalo, New York, and from E. reticulatus from Barrett and China Ponds near Carmel, New York.