 As a result of this combination, and precipitation of the large, complex molecule formed, the capsule appears to swell, because of increased surface tension, and its outlines become clearly demarcated.The pneumococcal quellung reaction was first described in 1902 by the scientist Fred Neufeld, and applied only to "Streptococcus pneumoniae", both as microscopic capsular swelling and macroscopic agglutination (clumping visible with the naked eye).It was initially an intellectual curiosity more than anything else, and could distinguish only the three pneumococcal serotypes known at that time.