The difficulty caused by the fragility of the ova of Ascaris lumbricoides.

The standard textbooks of clinical pathology and of laboratory technique describe the typical ova of Ascaris lunibricoides as being easily recognized, but all refer to the difficulty in recognizing certain of the ova. The following observation may explain why it is sometimes so difficult to recognize them. When searching for these ova it is convenient to work with relatively thick faecal emulsions and to make a preliminary search with a low power, a 1 in. or x 4 objective, because of their very typical appearance and relatively large size and colour. If an ovum is seen it can be centred and examined with a 2/3 or 1/6 objective to confirm its identity. Todd and Sanford's (1948) description of the typical fertilized ova is that