In 1900, Neufeld1 discovered that pneumococci in suspension were dissolved by adding bile to them.
Since that time, others have shown that solutions of the bile salts, i. e., sodium glycocholate and sodium taurocholate acted in the same way, and that whole bile was not necessary. In fact, there is evidence that the cholate part of the molecule is really the active part causing the lysis. This is one of the classic tests for the identification of pneumococci.
It is interesting to watch Neufeld's phenomenon under the high power of the microscope. To obtain this, mix a drop of pneumococcus suspension and a drop of bile salt solution on a glass slide, placing a cover-slip glass on it. The pneumococci gradually dissolve, becoming smaller and smaller. They pass through the stage in which they exhibit the brownian movement, and finally disappear.
Bile-solubility was found by Schilling2 and Neufeld1 to be