weeks or months of the appearance of the first symptoms. Such rapid cases are rare; more frequently the disease is an exceedingly chronic one, ebbing and flowing or slowly progressing through a long series of years.

Should serious ankylostomiasis occur before puberty, the growth and development are apt to be delayed and stunted.

Diagnosis.— Provided its presence be suspected, ankylostomiasis is easily diagnosed. In tropical countries, in patients coming from tropical countries, and in miners who work in very warm mines in cooler climates, anæmia with concurrent eosinophilia should always suggest a microscopical examination of the fæces. If the ova (Fig. 168, b, e, and Fig. 173) of A. duodenale or of N. americanus are discovered,*^[1] and no other reason for the anæmia be made out, the presumption is that one of these parasites is at the root of the mischief; at all events, no harm is likely to result from treatment based on this supposition. On the other hand, if no ova are found it must not be concluded that the case is not one of ankylostomiasis; for it sometimes happens that, in the later stages of the disease, symptoms will persist although the parasites which caused them in the first instance have disappeared spontaneously, or have been got rid of by treatment. Permanent degeneration of the alimentary canal, of the heart, liver, kidneys, and blood-forming organs, may remain, and even prove fatal, although the primary cause is no

1. ↑
   • Bass considers that by the usual microscopical examination of fæces quite 20 per cent, of infections with A. duodenale are missed; he recommends examination of fæces as follows: "A quantity of
   fæces is well diluted with water, 1 to 10, and strained through gauze to get rid of coarse particles. It is then centrifuged and the fluid poured off, the centrifuge tube being refilled and centrifuged again until all the diluted fæces have been used. The precipitate is rewashed several times with water as long as anything can be washed out. Calcium chloride solution of a specific gravity of 1050 is now added and the precipitate washed as before. This salt is preferable to others because of its hygroscopic properties, and its addition to the fæces disposes of everything having a specific gravity below 1050. The precipitate is now examined, and will be found to contain most of the eggs which were present in the whole amount of original fæces."