This was probably an exciting time for Blackley. He knew there was not much written about hay fever, and what was written was mostly speculation, so there was still a lot to learn about this newly defined disease.
By reading newspaper accounts, or perhaps by listening to his professors, he must have been well aware of all the recent investigations on microscopic substances. He most certainly would have known of recent studies on the reproduction of plants, and that it was determined plants reproduce sexually.
He must have learned about pollen, and how some plants were pollinated by bees and others by wind. He must have been well aware that pollen was in the air around him, and that a few physicians had speculated this pollen might be a contributing cause of hay fever symptoms, although it was never proven.
The idea that diseases could be caused by microscopic substances was proven by Louis Pasteur. Perhaps Blackley was thinking of this as he went to his bedroom one spring night. Perhaps he was symptom free when he opened the window to enjoy the refreshing breeze, but was sniffling and sneezing upon waking up. Perhaps it was this that caused him to have an aha moment.
Blackley and his friends spent many hours in enclosed rooms inhaling, sniffing, and rubbing onto their respiratory membranes and eyes and lips all the substances suspected of causing the symptoms. When none of them caused the symptoms of hay fever, they must have gotten excited that they were on to something truly historic here.
This excitement must have become exuberant when the first experiments on pollen came back positive for hay fever symptoms. The only frustration was when a test came back positive they had to wait for the symptoms to abate before performing the next test on himself.
However, even when he was having symptoms, he was able to study the types and quantities of pollens in the atmosphere. To do this, he constructed an apparatus (see figure) that allowed him to collect and count pollen for 24 hour periods in various locations "to imitate some of the conditions... to which a patient may be exposed in his daily routine." (1, page 122)
As he suspected to be the case, his own hay fever symptoms appeared to be worse on the days when the quantity of pollen in the air he was studying was highest. (1, 124-125)
By using his apparatus to count pollen on both hot days and cool days he was able to conclude that the quantity of pollen was determined by the temperature of the air.
Because he failed to measure the moisture of the air, he was unable to use his experiments with the apparatus to determine the effects of humidity on the release of pollen. So he opted to perform a separate experiment where he allowed several ears of rye to grow in a dry controlled environment, and several more to grow in a humid controlled environment. (1, pages 126-7)
The ears exposed to dry air threw off their pollen within a few hours, and the ears exposed to high humidity threw off no pollen. This test proved the release of pollen was greater on dry days than humid days. (1, pages 126-7)
By using his apparatus to collect pollen on rainy days, he quickly realized that rain was not conducive to the release of pollen. This explained why some hay fever patients observed a reprieve from hay fever when the rain was falling. (1, page 121)
However, he concluded: (1, page 86-87)
A high temperature is in itself favorable to the generation of pollen, but a high temperature with severe drought will, in the case of the grasses, check their growth, and thus prevent the formation of pollen. In proportion as temperature and moisture are suitably combined, so will be the production of pollen, but where these happen to be unusually favorable, we may have the grass arriving at maturity rapidly, and as a consequence this may be quickly cut and converted into hay and housed. Under such circumstances, hay-fever patients may have a short season of attack, but the symptoms may be very severe whilst they last. (1, pages 86-87)In the same manner, he proved that grass did not grow well at lower temperatures, and grass that did grow had less vigor. Likewise, plants that flowered prematurely, such as in March, did not have the same power as when the plant flowered in the middle of summer. (2, page 87)
Because pollen counts may peek during the dog days of summer, Blackley said he could understand how such an intelligent physician as John Bostock might confuse heat as the cause of the malady. Yet Backley now understood that heat was a contributing cause more so than the exciting cause.
He learned that the amount of wind affected pollen counts too. He said:
A quiet state of the atmosphere in the height of the hay season generally gave a large amount, but a strong wind lessened the quantity. In the latter case, however, if the wind was not very strong, I found the ophthalmic (tissue around the eyes) suffering to be more severe than in a quieter state of the atmosphere. (1, page 121)Various physicians recommended a visit to the city in order to obtain a reprieve from hay fever symptoms. While previous authors did not understand why this was so, Dr. Blackley proved by his experiments that it was because there was less pollen in the middle of a city. (1, page 121)
And, most notably, many physicians recommended hay fever vacations to the seashore at high altitudes, such as in the mountains. Dr. Morrill Wyman recommended hay fever vacations, particularly to the White Mountains.
- Blackley, Charles Harrison, "Experimental Researches on the Causes and Nature," 1873, London, Bailliere, Tindall, and Cox
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