Experiments with Dust and Pollen

Blackley was scientifically very observant. Once he reported on an attack caused by the dust cloud produced by a moving carriage on the road. Examination of the dust under the microscope revealed the presence of grass pollen grains. He concluded that "various channels by which a cause may reach a patient, in out of way places and at out of way times". On account of his ever alert and inquisitive mind, Blackley posed himself some questions: Can pollen produce the symptoms of hay fever? Does this property belong to all pollen? He also wondered if this condition is found in dried as well as in fresh pollen?

Subsequently the testing was done either by applying pollen to the mucous membrane, by inhaling it, by a decoction of pollen to the tongue or by inoculating the upper and lower limbs with fresh moistened pollen.

Very few scientists are aware that it was Blackley who first experimented with 'skin testing' for which he abraded a space of about quarter of an inch (c. 6 mm). Later pollen was applied after being placed on a piece of wet lint, the size of the abrasion, and was held in position by a strip of adhesive plaster. Scratching with a lancet, raised a weal such as seen in urticaria... Blackley concluded that the action of the different pollen grains was not related to their size, shape, roughness or to the poisonous character of the family. Later he hypothesized on the possible involvement of alkaloid in hay fever.

He undertook a series of experiments to establish the relationship if any, between the quantity of pollen found in the air and the intensity of symptoms.

Blackley used kites to collect airborne pollen at great heights. Of course, he found that kites were by no means as easily managed as first expected and he had many failures and disappointments.

He used a kite 6 inches in length and 3 inches in width. It had a central shaft (standard) and a semicircular top (bender). For covering the kite he used thin tissue, waterproofed with a mixture of boiled linseed oil and copal varnish. The kite carried a special slide holder. In this first experiment done in June 1868, his kite could reach an altitude varying from 90-150 m. On analysis of the slides he found the quantitative proportions of pollen in the upper strata were largely in excess of that of the lower strata (104:10). He repeated his experiment with a kite a year later when his kite with a slide could reach heights varying from 180-240 m capturing a total of 580 in contrast to 16-64 pollen at ground level. On an average he found 19 times more pollen in the upper level as compared to the ground level.

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