Dr. A. Pfeiffer has recently contributed an interesting paper relating to the insufficiency of chemical processes for purification of sewage, to a German sanitary paper. In a general way he reviews the different methods that have been adopted for the chemical purification of sewage, and points out the dangers of the irrigation method of sewage disposal. It is now understood that the great danger from sewage water lies in the microörganisms that infest it, and Pfeiffer asks if the modern methods of purification as applied to the waste of towns and cities, have any real effect in clearing the sewage of these microörganisms.
We know, of course, that carbolic acid, bichloride of mercury, and other chemicals kill germs, but we know also that we cannot apply them on any very extensive scale. We cannot make the sewage strongly alkaline nor acid in order to destroy the microörganisms, because the fish