196 BACTERIA AND SOIL FERTILITY 



the fish soon dies. Death in this case is not due to a lack of food, 

 as a similar fish placed in distilled water lives for some time. 

 Now, if a small quantity of calcium chloride had been added to 

 the first solution the fish would have lived normally. Moreover, 

 if the heart be removed from the body of a cold-blooded animal 

 and placed in a salt solution it soon dies, but if a small quantity 

 of calcium salt be present the heart beats normally for some time. 

 When one salt thus counteracts the poisonous effect of another it 

 is spoken of as antagonism and a solution made up of a mixture 

 of salts such that there is no toxic effect is known as a balanced 

 solution. 



This property of antagonism also exists with regards plants. 

 One may take a soil which contains sufficient common salt to be 

 injurious to plant life and overcome the toxicity by adding cal- 

 cium salts to it. This appears to be a general law, as the injurious 

 action of sodium carbonate, sodium sulfate, and a number of 

 other salts toward bacteria can be neutralized by the use of cal^ 

 cium salts. The extent to which this neutralization can be car- 

 ried is limited, as it is only the less concentrated salts which can 

 be thus neutralized. However, this does indicate that a concen- 

 tration of a single salt is often more injurious than is a similar 

 concentration of several salts. We, therefore, have the peculiar 

 phenomenon of being able to reclaim some alkali soils by adding 

 more alkali to them. 



Numerous workers have attempted to explain this peculiar 

 phenomenon. Even before ideas on anta2:onism had taken a defi- 

 nite form, Loew elaborated a theory to account for the toxic 

 properties of magnesium when calcium was not present in suffi- 

 cient quantity. He supposed calcium to be a necessary constituent 

 of the chlorophyll bodies and nucleus, and when magnesium is 

 present in great excess this takes the place in those bodies which 

 should be occupied by calcium. This caused a structural distur- 

 bance on account of which the protein substances cease to be 

 active and death ensues. It will be observed that this will only 

 explain the need for a balance between calcium and magnesium 

 and not between other compounds, as is often the case. Osterhout 



