234. INTESTINAL BACTERIA 
destroyed some essential substance. Levin (1899, 1904) found the in- 
testines of most Arctic animals completely sterile. He draws no con- 
clusions, but his work is of interest on account of normal growth without 
bacteria. Metchnikoff (1901) grew tadpoles in sterile bread and water 
and secured no transformation into frogs in either the sterile or unster- 
ilized tadpoles. The non-sterile grew larger than the sterile. Portier 
(1905) determined that larve of certain lepidoptera lived aseptically. 
Moro (1905) confirmed the work of Schotellius which has been men- 
tioned above. He used turtles instead of chicks. Bogdanow (1908) 
concluded that bacteria were necessary for normal development because 
sterile larvee of piptera did not do as well as those kept in an unsterile 
environment. Wollman (1911) criticized the work of Bogdanow, 
stating that his sterilization was carried out at too high a temperature. 
He concluded from his work on flies that bacteria were not necessary 
for normal development. Cohendy (1912) thought that the digestive 
processes could proceed without bacteria, but that they aided digestion. 
Life was thought to be possible without bacteria, but bacteria are not 
indispensable. Kianizine (1915) produced data which he thought 
weakened the argument of Cohendy. With chickens, Kianizine believed 
that bacteria were of great aid in digestion. They carried on analytic 
and synthetic processes which were of much value to the host. Ina 
later paper by the same author (1916) he continues his argument. He 
made guinea pigs breathe sterile air and eat sterile food and found that 
even after a few days they were greatly weakened. The bad results 
from the deprivation of bacteria was thought to be due to reduced 
oxidation and accumulation of leucomaines in the body. Loeb and 
Northrop (1916-1917) attempted to determine the ability of flies to 
synthesize their body proteins without the aid of microorganisms. 
Larvae grown on sterile media (banana) did not do well, while those 
placed in a sterile yeast culture developed normally. It was thought 
that yeasts were essential for this species of fly although the essential 
element could not be isolated. 
This rather extensive presentation of the literature gives the data 
from which our present conclusions must be drawn. Obviously much 
of the data which have been used cannot be applied to conditions in the 
human intestinal tract. 
Action of Bile on Bacteria. This juice is poured into the intestine 
just below the pylorus. It isa thick liquid with a decidedly bitter taste. 
It is made up of salts of glycocholic and taurocholic acids, pigments 
(bilirubin, biliverdin, etc.) fats, phosphatids and inorganic salts. 
The bile like most of the other body fluids is probably sterile when 
