Cell block techniques employed in parallel or instead of smear preparations are used in many laboratories to examine cytologic material and to bridge the gap between cytology and histology.8 The advantages of this approach, either when agar4 6 or when plasmathrombin23 is used for entrapping cells are that, without loss of the fine cytologic characteristics, the histological arrangement of cell clusters can be appreciated. Additional advantages include lack of overlapping or obscuring by blood or other debris which makes reading of smears difficult.The celloidin film, which forms a semipermeable membrane around the sediment, allows dehydration and embedding in paraffin but not the escape of cells nor, even more dangerous for the diagnosis, the entry of "floating" cells. We found the "cell-bag" technique faster and easier with definite advantages over the agar or plasma-thrombin methods. In addition, there was no dispersion of the sediment and the cells remained grouped. This technique was applied with success on cytologic material from various sources and may be applicable in other fields such as endometrium.A definite diagnosis with histological typing was reached in 74% of carcinoma of the lung. Falsenegative diagnoses (26 %) were related to extension of necrosis and to lack of viable cells. No false-positive caseswere observed. Theseresultscompare favourably with those obtained by other procedures.8 The number of the present cases is, however, too small to allow a definite evaluation of the relative advantages of the"cell-bag" technique over theconventional smear procedure, and is a matter for future studies.The results obtained on cytologic material from various sources indicate that embedding of the sediment in a celloidin film is a simple and reliable procedure, and can be helpful in the investigation ofcell clusters and tissue fragments.

Ninety-six cases of extraurinary schistosomiasis due to Schistosoma haematobium were encountered in a retrospective histopathological study of cases encountered over a period of 12 years in Southern Iraq. Seventy-six cases involved three main systems, namely the female genital system (29 cases), male genital system (15 cases) and the lower intestinal tract (32 cases). In the remaining 20 cases unusual sites such as lymph nodes, skin, liver and lungs were affected. In none of these cases did the clinician initially consider schistosomiasis to be the cause of the patient's illness prior to the histological diagnosis.

The technology of scanning electron microscopy (SEM) is described in brief. Its application to the study of cell and tissue structure is demonstrated and the evolution of the concept of "topographical histology" is discussed. Some current literature on the application of SEM is reviewed under the headings of experimental pathology and human pathology. While SEM has become an indispensable technique for the experimental morphologist, its application to diagnostic pathology and cytology is still at an early exploratory stage.

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