Myers and Voegtlin (14) report that they have been able to remove the anti-neuritic substance from autolyzed yeast by means of its solubility in olive oil or in oleic acid. They state that it is also soluble in acidified methyl alcohol, and can be extracted from unautolyzed (dry) yeast by this solvent.

It will be seen from the foregoing, that but little progress has been made in devising methods for accumulating considerable amounts of the anti-neuritic substance or for determining its identity. There are other confusing factors which enter into studies of this character and which are not generally appreciated. One of these is that the results of several investigators have indicated that compounds of several kinds, including purins, pyrimidins and pyridins, have induced at least temporary "cures" in pigeons suffering from polyneuritis. Still more recently Dutcher (15) has reported "cures" of pigeons as the result of administering such physiological stimulants as adrenalin and pilocarpin, both of which are absent from all ordinary foods.