Hay fever : its causes, treatment, and effective prevention : experimental researches / by Chas. Harrison Blackley.

Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: Hay fever : its causes, treatment, and effective prevention : experimental researches / by Chas. Harrison Blackley. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    the average weight of the pollen grains of several species of plants was ascertained. In each case.ten slides were counted, in order to neutralise possible errors. Ten slides of the pollen of Lolium perenne had an average of 150*8 on each slide; thus it was found that one grain, by weight, of this pollen would contain 6,032,000. Ten slides of the pollen of Plantago lanceolata contained 253*1 on each slide, so that it would require 10,124,000 to make up one grain by weight. Ten slides of the pollen of Scirpus lacustris gave an average ' .of 620-5. Thus one grain by weight would contain 24,820,000 pollen grains. The pollen of the Vacoa (an exotic) contained 37,888,000 in one grain. § 386. It is necessary to remark here that the weight of the single pollen grain differs in different years. In a number of experiments tried in 1874, one grain of the Lolium perenne was found to contain 4,400,000.* At § 276 I remark, that' in addition to those influences which make pollen more or less capable of fulfilling its own proper function in the vegetable world, there also seems to be some influence at work which, independent of the quantity of the materies morbi, or condition of the patient, alters its power of producing hay-fever.' I believe now that this difference is mainly owing to the difference in the size of the pollen grain, and that this again is dependent upon the kind of season. In late and cold seasons, such as we had last year (1879), we shall have ill-developed pollen. In warm seasons we shall, on the contrary, have large and vigorous in diameter, is now made to touch the points of the screws K K k, and the fluid will at once be distributed over the surface of glass within the ring of varnish. The slide is now placed in the horizontal position, and kept at a temperature of 100° or 120° Fahr. until the alcohol and water have evaporated and the glycerine is left as a thin and smooth layer. By placing the slide under the microscope with a good £ in. or ]• in. objective of moderate angle, the pollen grains can easily be counted on any microscope that has a mechanical stage attached to it, if the method described at p. 155 is followed. * In an article sent to Dr. Zuelzer of Berlin (in 1876), and from which I believe some extracts were published in the new edition of the second volume of Ziemssen's Cyclopedia of the Practice of Medi- cine, the calculations were based on these numbers (4,400,000). 16—2