Trichomonas muris infections were encountered in the oxyurid nematodes Aspicularis tetraptera and Syphacia obvelata parasitic in laboratory white mice. More rarely infections with other protozoa were encountered in the helminths. The distribution of both protozoan and helminth infections was studied, and the incidence of infected helminths determined. Dividing forms of Trichomonas muris occurred in the intestine of the worm as well as free in the lumen of the intestine of the mouse. An interpretation of certain findings in dividing forms is offered.

Rhabditiform first-stage larvae of Nippostrongylus muris are about 270–550μ long. The development of these larvae culminates in a moult, which occurred 36–48 hours after cultures were prepared. The first moult is preceded by an unusually early separation of the first cuticle, which is fine and unstriated, from the body tissue in the tail region and, later, by the formation of an underlying new cuticle, which is thicker and prominently striated.

Early second-stage rhabditiform larvae differ in certain morphological respects from first-stage larvae. Second-stage larvae are about 470–750μ long.

A second preparasitic ecdysis occurs and the infective larva is a true third-stage larva. This moult was the only one previously known to occur during the preparasitic development of N. muris.

The post-cervical cuticular inflation in N. muris is regarded, on the basis of a comparative study of the cuticle of this species and of Haemonchus contortus and other trichostrongyles, as resulting from the separation of the second and third layers of the cuticle. Yokogawa's view that Nippostrongylus muris has two cuticulae is rejected. N. muris has a single cuticula, apparently made up of four layers.

N. muris undergoes four complete moults and the development of this species does not differ in any essential respect from that reported for other strongyles.

Morphological, histopathological, and immunological studies of seven strains of rickettsial disease have placed them in two widely separated groups, for which typhus and spotted fever seem the most logical names.

Diseases of the spotted fever group are carried by ticks (Arachnoidea) and characterised by distinctive histopathological lesions—thrombonecrosis of arterioles and venules, with micro-organisms of definite and characteristic morphology, invading smooth muscle cells, as well as endothelium, mesothelium, and macrophages. Tissue culture studies show massive invasion and distention of cell nuclei, while cytoplasmic invasion of host cells is relatively sparse.

Diseases of the typhus group are carried by lice and fleas (Insecta) and characterised by the facts that the intracellular parasite which causes them invades only endothelium and mesothelium, distends the cytoplasm of its host cells without ever invading nuclei, and in guinea pigs causes only proliferative endangeitis without thrombonecrosis.

In the spotted fever tick, organisms are intranuclear as well as intracytoplasmic, invade nearly all types of tissue, and are transmitted hereditarily. In typhus-infected lice and fleas, organisms are intracytoplasmic only, infect only the lining cells of the gut, and are not transmitted hereditarily.

Neither focal brain lesions nor scrotal sac exudation is of importance in the differential diagnosis, since both occur in certain strains of spotted fever, as well as in typhus. Definite necrosis of the scrotum is of importance, since it is dependent upon the above-described arteriolar thrombonecrosis and is peculiar to spotted fever.

A review of the literature shows that rickettsial diseases and their etiological agents are being classified in an inaccurate and unjustifiably complex manner, specific names often being given to organisms without the presentation of evidence sufficient to establish them as new varieties.

A plea is made for the study of unclassified or unsatisfactorily classified diseases in all parts of the world by the methods described, and for their classification on the basis of morphologic and histopathologic observations on insect and mammalian hosts and of immunological studies on the latter, rather than on variations in clinical pictures in man and in experimental animals.

The criteria for the differential diagnosis between typhus and spotted fever are presented in tabular form and illustrated wherever possible. All reported rickettsial diseases as well as their etiological agents are classed on the basis of the criteria presented, and, with the exception of the incompletely studied mite-borne group, the available evidence strongly suggests that all are varieties of typhus and spotted fever.

The morphological, histopathological, and immunological differences between typhus and spotted fever are so great that these two diseases, as well as their causative organisms, should be widely separated from one another, and given definitely distinguishing names.

It is suggested that the well-established name, Rickettsia prowazeki, be applied to intracytoplasmic micro-organisms in Insecta causing all diseases of the typhus group, and that Dermacentroxenus rickettsi (the name originally given by Wolbach) be applied to hereditarily transmitted micro-organisms invading nuclei in Arachnoidea and in tissue cultures, causing all diseases of the spotted fever group. Specific varieties, when established by the demonstration of definite and constant biological differences, should be indicated by variety names, as Rickettsia prowazeki mooseri (for endemic flea-borne typhus in all parts of the world).

The commonly accepted view regarding the manner of entry of larvae of Wuchereria bancrofti (Cobb.) into the body cavity of its mosquito host is that microfilariae from human blood enter the stomach of the mosquito along with the blood meal and after casting their sheath in the stomach, they penetrate through the wall of the stomach, enter the haemocele and then find their way into the thoracic muscles. The time taken for the penetration of the stomach wall according to Looss (1914) is 6–12 hours. According to Bahr (1912) the worms appear in the thoracic muscles in 24 hours, while Lebredo (1905) recorded that in exceptional cases, worms were seen in the thorax 13 hours after feeding, but ordinarily the time interval was longer.

Three pure-line strains started from single individuals, 2 of Trichomonas and 1 of Eutrichomastix, all from snakes, were isolated from mixed cultures. These strains, and another of Eutrichomastix from a chamaeleon, were under observation for periods of from 3 to 10 weeks.

The Eutrichomastix of snakes does not differ from that of the chamaeleon in any essential point, and neither developed an undulating membrane at any time during this prolonged period of observation.

The Trichomonas of the grass-snake is morphologically distinct from that of the boa. Trichomonas of the boa has an ill-developed undulating membrane with only a few shallow waves, and may simulate a Eutrichomastix owing to the accidental detachment of the bordering flagellum.

Trichomonas from snakes, as from most other hosts, readily feeds upon starch granules, whereas none of the Eutrichomastix were found to ingest unaltered starch.

Eutrichomastix from snakes and the chamaeleon never develops an undulating membrane and does not assume a Trichomonas form.

From these observations it can be definitely concluded that Trichomonas and Eutrichomastix are generically distinct.

Trichomonas sp. from a corais snake

Description. Body usually pear-shaped. Average size 12 × 8μ, Three anterior flagella of unequal length. Basal fibre absent. Feebly developed undulating membrane.

Habitat. Intestine of Dymarchon corais, from North America.

Locality. London.

A Eutrichomastix morphologically identical with E. serpentis (Dobell, 1907) Kofoid & Swezy, 1915, is described from 3 species of African snakes, namely, Psammophis sibilans, Boaedon lineatus and Crotaphopeltis hotamboeia.

The morphology and life cycle of an amoeba producing amoebiasis in reptiles is described. The organism is assigned to the species Entamoeba invadens Rodham 1934, because of the pathogenicity of that species.

Material for the study was derived from 30 individuals of 7 species of reptiles, either dying of spontaneous amoebiasis or experimentally infected. (Material from 3 additional species of reptiles dying of amoebiasis was not used in this study.)

With the exception of a few minor morphological differences, E. invadens was found to be strikingly similar to E. histolytica in morphology of trophic and cystic stages, and in the processes of encystation, excystation, and metacystic development.

Metacystic development was studied in stained preparations made from the intestines of snakes 1–24 hours after the inoculation by mouth of mature cysts. Excystation usually takes place in the jejunum and ileum, a single quadrinucleate amoeba hatching from each cyst. Each quadrinucleate metacystic amoeba ultimately forms 8 amoebulae as a result of one division of each cystic nucleus, cytoplasmic division, and parcelling out of the cystic (N) and daughter (n) nuclei. Nineteen of the 24 possible combinations of N and n nuclei were observed.

The culture phenomena of multiple fission without encystment is suggested, and cannibalism of cysts by the trophozoites is described.

The description of Sphyranura oligorchis (Alvey, 1933) and S. polyorchis n.sp. is presented together with an account of the development of the former. Study of the life history of S. oligorchis, and a review of the literature on the life cycles of the Monogenea, show that at a corresponding time in their development embryonic stages similar to Dactylogyrus are present. It is postulated that Dactylogyrus is near the primitive ancestral type of the Monogenea, and that all of the parasitic platyheminthes may have arisen from a common planula ancestor.

1. A specific disease of cattle is described which occurs sporadically in the East Coast fever areas of eastern equatorial Africa. Clinically, acute cases are characterised by peculiar nervous symptoms, absence of fever and blindness. Death occurs in most cases within 2 to 21 days of the onset of illness. Chronic cases are encountered from time to time and may survive up to 6 months.

2. The disease is widespread in Uganda. It affects cattle of both sexes and all breeds, and is commonest in young stock between 6 months and 2 years of age. It has, however, been observed in older animals.

3. Pathologically, in acute cases petechial haemorrhages or extravasations are found in various parts of the brain and meninges. Generally the haemorrhages are small and do not seriously injure the adjacent brain tissue. In some cases the extravasations are responsible for a considerable amount of damage.

4. Microscopic examination shows that the brain lesions are due to extensive embolism of cerebral vessels. The lymphocytes which form these emboli contain in their cytoplasm protozoan bodies indistinguishable in structure from the schizonts of the genus Theileria. These bodies occur in great numbers in the brain, but are extremely rare or absent in the lymphocytes of other parts of the body.

5. In chronic cases the haemorrhages have been absorbed but the brain is permanently damaged by replacement changes, and by the appearance of small cysts or cavities which contain a citron-coloured fluid. These cavities when numerous seriously disorganise certain parts of the brain.

6. The disease has not yet been transmitted experimentally, and its connection with the theileriases is still uncertain. However, much evidence has been collected to show that cases of turning sickness have been infected with East Coast fever some time previously, generally on an average of 6–8 months.

7. The possible relationship between turning sickness and East Coast fever is discussed at some length during the course of the paper.

A bacterial organism is described which occurs constantly in Rhodnius prolixus. It is present in the unfed newly hatched insect inside the cells at the cardiac end of the mid-gut. Some days after feeding, the bacteria are set free into the cavity of the gut and multiply in the undigested blood in the stomach. They are ultimately digested in the intestine.

Morphologically they resemble diphtheroid bacilli in being highly pleomorphic and in giving rise to thread-like forms in old cultures.

Preliminary experiments with Lucilia larvae by Dr R. P. Hobson, suggest that when blood is infected by this micro-organism it contains “vitamin B” and becomes an adequate diet for insect growth.

These observations support the view that symbiotic organisms in exclusively blood-sucking insects provide an endogenous source of vitamin.

Anguillulina Aptini (Sharga) was described in 1932. Nematodes had previously been recorded in other species of thrips (Uzel, 1895; Russell, 1912), but no descriptions had been published. There is an extensive body of literature dealing with the nematode parasites of other insects (see van Zwaluwenburg, 1928).

A list of entomophagous fungi was published by Gray in 1858, and since then a great many more have been recorded. Accounts of those found in the body cavity of scale insects have been given by Schwarz (1924), and by Brues & Glaser (1921). These are apparently symbiotic and allied to Saccharomyces. Several species of Coelomyces have been found in the body cavity of mosquito larvae and described by Keilin (1921, 1927) and Iyengar (1935).