Pollen Analysis Circular The last issue of the "Pollen and Spore Circular" (#18) was edited by Calvin J. Heusser and announced the fusion, indicating that "the spore and pollen section will constitute four to six pages in each issue and contain essentially the same material" as in the "Pollen and Spore Circular". The final issue also included abstracts from the First Palynology Conference (February 25, 1953), held at Yale University as well as correspondence from researchers working as far afield as Düsseldorf, Lucknow, and Indianapolis. It was in the pages of the "Pollen Analysis Circular" that the field of pollen analysis was given
Enteric coating However, as the solvents for such solutions are organic solvents, there's a concern about the toxicity potential of the traces of the residual solvents in the tablet coating. The first form of gastro-resistant coating was introduced by Unna in 1884 in the form of keratin-coated pills, although it was later discovered that they weren't able to withstand gastric digestion. Salol was also used by Ceppi as one of the first forms of enteric coating. However, the first material that was extensively used as enteric coating agent was shellac, since its introduction in 1930. Properly treated or hydrolyzed shellac showed different