EXPERIMENT STATION REPORTS. 153 



REPORT OF THE BAOTERIOLOGIST. 



Director R. S. Shaw: 



Dear Sir: — Let me present the work of this division of the experiment 

 station for the past year under the following headings: 



(1) General Bacteriology. (2) Soil Bacteriology. (3) Dairy Bacteri- 

 ology. (4) Pathogenic Bacteriology. (5) Commercial Bacteriology. 



GENERAL. BACTERIOLOGY. 



Under this heading, I desire to submit the paper prepared by Dr. 

 Otto Rahn entitled, 'The Fermenting Capacity of the Average Single 

 Cell of Bacterium Lactis Acidi," Avhich is printed elsewhere in this 

 report as Technical Bulletin No. 11. This paper is the result of study 

 and experimental work over a period of several years. While the sub- 

 ject does not deal with any immediate and direct application to agri- 

 culture, it is, however, of fundamental interest and use to workers in 

 the field of microbiology, and will doubtless prove essential to the 

 proper development of applied problems. 



SOIL BACTERIOLOGY. 



This work is under the immediate charge of Dr. Otto Rahn, who has 

 associated with him W. A. Wentworth. The work is in progress, but 

 at this time no results are submitted. Dr. Rahn, however, makes this 

 statement regarding his work : 



"The main problem in soil bacteriology is the role of microorganisms 

 in the building up of farm land from the two extreme soil types of 

 Michigan ; the barren sand of the jack pine plains and peat. The sand 

 is ])ractically free from organic matter, the peat contains hardly any- 

 thing but organic matter. Both these soil types are very common in 

 Michigan. 



It seems reasonable to suppose that more can be learned hy follow- 

 ing closely the building-up process of a soil than by starting with a 

 good farming soil. This main yu'oblem involves the formation of humus 

 and the decomposition and availability of peat compoimds as well as 

 the peculiarities of peat as a soil. The experiments were begun in the 

 spring of 1910. 



The soils and soil mixtures under study are in large sunken cylinders 

 with open bottom, 4 feet deep and 2 feet in diameter. The cylinders 

 were cropped and treated in various ways. The old idea that peat acts 

 as an antiseptic was easily disi)roved by a few experimeuts on bacterial 

 activity in peat. Peptone was decomposed to ammonia, and ammonium 

 salts were oxidized to nitrates without retardation, if sufficient moisture 

 were provided. The so-called "disinfectant qualities" of peat consist 

 probably in nothing more than its great water capacity, and its ready 

 absorption of disagreeably-smelling compounds, such as ammonia, skatol 

 and other products of putrefaction. This is apt to make tlie layman 

 believe that such decomposition does not take place. 



