IOWA ACADEMY OF SCIENCES. 81 



there is an organic impurity, the bacteriologist can tell what the impurity is. 

 Bacteriologists have made many analyses of water and sewage. The methods used 

 are still open tor improvement. Water analysis is indeed a difficult problem. 



Prof. Sedgwick,"' in an exhaustive treatise on purification of water and sewage 

 in report of the Massachusetts State Board of Health, says: "Although microscop- 

 ical analyses (so-called) of water or sewage have often enough been undertaken the 

 methods employed have hitherto been so imperfect that little importance has been 

 attached either to the examinations themselves or to the results." 



There are two ways in which water may be examined: First, microscopically; 

 second, cultures. The former was the method chiefly in vogue before the use of 

 the Koch system of cultivating germs. This method was employed by Cohn '"^ and 

 Radelkofer "' in making examination in Breslau and Muenich. The bacterial exam- 

 ination of water requires cultures, and this is a very important part of the work. 

 But I do not believe that culture examination is sufficient for this work. The 

 Massachusetts State Board of Health employed Dr. Sedgwick, a well known 

 authority in biological research, to make a biological study of sewage and drink- 

 ing water. A new method was introduced as the combined work of Kean. Sedg- 

 wick and Rafter"^ which makes it a comparatively easy matter to determine 

 approximately the microscopical organisms. 



Jcergensen"*' has well stated that the exclusive use of gelatine in this branch of 

 biology may introduce sources of error. Hansen's work, as well as that of Joergen- 

 sen, was more especially intended for zymotechnical purposes, and yet I believe 

 it is equally applicable in hygiene. It may be well to start a series of cultures in 

 small flasks that contain sterilized sewage or water'with some organic matter. For 

 a study of these germs the Hansen method may be used. I believe that good 

 results may be obtained by using liquid media. Miquel's" work certainly 

 shows good results. The use of the fermentation tube, as suggested by Dr. Theo- 

 bald Smith, •= is a most excellent device. Many of the bacteria found in faeces are gas 

 generators and by use of the fermentation tube which contains bouillion and 

 sugar, the kind and quantity of gas produced may be determined readily. Stoller'* 

 has recently used this apparatus extensively with some success in arriving at the 

 quantity of faecal bacteria in water. 



The most important methods in bacteriological examination of water are those 

 of the Koch school. In this method a known quantity of water, a fraction of a 

 cubic centimeter is put in gelatin or agar and the number of germs which develop 

 are counted. Obviously the smaller the fraction the more danger there will be of 

 making errors in giving the result of the number of germs per cubic centimeter. 



'5 A reporter the Biological work of the Lawrence experiment station of Massachu- 

 setts State Board of Health, 1888-1890. 



^sUeber den Brunnenfaden (Chrenolhrix polyspora) mit Bemerkungen ueb'er die 

 Mikroscopische Analyse des Brunnenwassers, Beitraege zur Biologle der Pflanzen 

 I, p. 108 Breslau 1870. 



"MikroskopischeUntersuchung der Organlschen substanzen im Brunnenwasser, 

 Zeitschrift fur Biologie I (1865), p. 26. 



•8 Experimental investigations, Mass. State Board of Health, 1888, 1890, Pt. II, pp. 

 803. 811. Recent Progress in Biological Water Analysis, Journal of the New England 

 Water Works Association. September 1889. The Biological Examination of Potable 

 Water, Proceedings Rochester Academy of Sciences, 1890. 



'OL c, p 48. 



"Annuaire del' Observat.oire de Montsourls 1877-1890. Not seen in the original. 



'SOentrallblatt bur Bakterlologie und Parasltenkunde. Vol. VII, p. 302. and Vol 

 XII, p. 367. 



"3Sclence, Vol. XXII, No. 564, p. 286. 



