"
Mr. Blackley had little difficulty in determining that the cause of his
trouble was the pollen of grasses and flowers, and his investigations
showed that the pollen of some plants was far more irritating than the
pollen of others. The pollen of rye, for example, produced very severe
symptoms of catarrh and asthma, when inhaled by the nose or mouth. Mr.
Blackley came to the conclusion that the action of the pollen was partly
chemical and partly mechanical, and that the full effect was not produced
until the outer envelope burst and allowed of the escape of the granular
contents.
Having satisfied himself that pollen was capable of producing all the
symptoms of hay fever, Mr. Blackley next sought to determine, by a series
of experiments, the quantity of pollen found floating in the atmosphere
during the prevalence of hay fever, and its relation to the intensity of
the symptoms. The amount of pollen was determined by exposing slips of
glass, each having an area of a square centimeter, and coated with a
sticky mixture of glycerine, water, proof spirit, and a little carbolic
acid. Mr. Blackley gives two tables, showing the average number of pollen
grains collected in twenty-four hours on one square of glass, between May
28 and August 21, in both a rural and an urban position. The maximum both
in town and country was reached on June 28, when in the town 105 pollen
grains were deposited, and in the country 880 grains.
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