No 
S) 
oS 
LORANDE LOSS WOODRUFF 
I. GENERAL INTRODUCTION 
Although hay infusions have been one of the chief means of 
providing organisms for microscopists from the early days of 
Leeuwenhoek, there are comparatively few published data which 
have been secured through a careful study of the origin, relative 
number, and sequence of the various organisms which abound in 
them. It is a well known fact that a hay infusion presents a 
kaleidoscopic series of phenomena from its inception until it 
finally reaches a stage of sterility, or, in the presence of sunlight, 
of practically stable equilibriumin which animalsand green plants 
become so adjusted that a veritable microcosm exists; and it is 
also generally accepted, largely on the basis of casual observation 
of infusions made up for one purpose or another, that the organ- 
isms appear and disappear in quite a regular sequence. 
It seemed desirable, accordingly, to attempt to study the fauna 
and flora of representative infusions by some comparatively exact 
methods. The first intention was to make a comprehensive tabu- 
lation of the entire animal and plant life of the infusions studied, 
including bacterial counts, as well as to follow the chemical and 
physical changes in the medium. This proved to be impossible 
without the aid of more assistance than was available.1 Conse- 
quently the study was chiefly confined to a careful observation of 
the Protozoa which appeared, and especially to certain charac- 
teristic forms which were present in large numbers in practically 
all the infusions studied. 
This general problem has been considered by Peters,? but more 
data were needed for points of attack on the biological effects of 
one type of organism on another, and this survey of the protozoan 
1 Certain chemical analyses, chiefly in regard to the acidity of the infusions, were 
made by Dr. M.S. Fine, and his results are published independently in the follow- 
ing paper, in this journal, entitled: Chemical Properties of Hay Infusions with 
Special Reference to the Titratable Acidity and its Relation to the Protozoan 
Sequence. 
2 Metabolism and division in Protozoa. Proc. Amer. Acad. Arts. and Sci., vol. 
39, no. 20, 1904. Chemical studies on the cell and its medium. !. Methods for 
the study of liquid culture media. Amer. Journ. Physiol., vol. 17, no. 5, 1907; 
11. Some chemico-biological relations in liquid culture media. Amer. Jour. 
Physiol., vol. 18, no. 3, 1907. 
