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Studies on human trichinosis have shown that eosinophilia is so constantly associated with trichinosis that its presence may serve as an important factor in the diagnosis of the disease. Considerable variation occurs in the degree of eosinophilia and the length of time it persists. There is a pronounced leucocytosis and eosinophilia in human infections. Cases with no eosinophilia but with a general leucocytosis are cited by Conner (1929) as an atypical form of trichinosis. Although the haematologic response of man to infections with Trichinella spiralis is quite well established, the same cannot be said of a number of laboratory animals that are used a great deal in experiments on this parasite. Maass (1933) made blood counts on trichina infected hogs. Of nine animals with normal blood pictures, two each were fed 100, 200, 1,000, and 2,000 encapsulated trichinae from muscle; the ninth pig served as a control. Eosinophiles increased gradually beginning a few days after infection; reached a maximum in 20 to 24 days (that is when the young trichinae penetrated the muscle) constituting 10, 12.5, 20, and 27 per cent, respectively; then fell rapidly, and gradually returned to normal within two or three days. Eosinophilia in the control animal varied irregularly from 0.5 to 4.5 per cent. At autopsy all the hogs that had been infected showed trichinae, particularly in the diaphragm, and also in the cheek, thoracic and the thigh muscles. The eosinophilia described by Maass was accompanied, in every case, by a leucocytosis in proportion to the number of worms ingested. In monkeys McCoy (1932) was unable to demonstrate a marked eosinophilia in his experimental work. Wantland (1937) studied the blood in normal and trichina infected white rabbits and found that variations occur even in normal animals, but in rabbits infected with 5,000 to 10,000 larvae a leucocytosis developed from the second week after infection. The animals that showed the severest symptoms also showed a greater eosinophilia; however he concluded that the percentage of eosinophiles was not an index of the severity of the infection. Van Someren (1938) in a series of differential counts on rats, both

IN any study requiring the assessment of quantitative changes of a particular cell type in a suspension of mixed marrow elements, a method is essential whereby these cells may be counted with a known degree of accuracy. This problem was encountered in experiments designed to investigate the possible presence of a factor in pernicious anaemia serum affecting the rate of maturation of erythroblasts cultured in vitro, as reported by several workers (Rusznyak et al 1947, Lajtha 1950, Thompson 1950). Our results are presented elsewhere (Feinmann, Sharp and Wilkinson, 1952). In these experiments it was necessary to count absolute numbers of certain erythroblasts to a known degree of accuracy in order to determine whether observed differences in changes in their numbers on culture in different media were significant. The method of counting is described in detail since, with suitable modification, it has more general application. When it is not possible to count directly the number of cells in a known volume of fluid, the absolute number of a cell type per unit volume is derived by determining its proportion on smears and relating this to the total cell count. It is well known that in smears prepared on slides, the larger cells appear more frequently at the ends and edges of the smear than in the centre (Stephens et al 1920, Napier 1922, Gyllenswaird 1929, Boveri 1939, Dacie 1950). Methods of sampling of the slide, giving reasonably constant estimates of the proportion of a cell type on smears from one blood sample, have been devised (Dacie 1950). Our problem required the assessment of proportions of normal and megaloblastic erythroblasts in a marrow suspension, initially and after a period of incubation; during this incubation there might be not only a change in the relative propor

Neutrophilic lung infection and inflammation are typical for CF but have also been reported in preschool children with recurrent wheeze. We therefore compared BAL results in 143 symptomatic preschool (