4/6 ISHIZUKA ; ON THE SIGNIFICANCE OF THE NITRATES 



Moreover, shallow soils are more easily deprived of the 

 nitrates by the same amount of rain than deep soils ; and final ly 

 a great influence will be exerted by the temperature, as in sum- 

 mer the nitrification is more intense than in winter. Thus we 

 observe a local and temporal influence upon the amount of nitrates 

 present in the soil, and the great differences Bcrtlielot (l) observed 

 in regard to the quantity of nitrates in plants thus finds a simple 

 explanation. 



Countries with regular and copious summer rains will show 

 also less nitrates in the plants than countries with rather dry 

 summers, while again in desert-soils nitrates are not found at all, 

 because of no bacillus being able to thrive in the absence of 

 water. 



The noxious qualities of vegetable food, rich in nitrates, for 

 animals have been recognized by Lawes and Gilbert, the illu- 

 strious investigators of Rothamsted, England. I quote from the 

 lecture of Henry Gilbert delivered in America in Nov. 1893 the 

 following passage : 



" Then, again, as generally more or less of the 

 nitrogen in root will exist as nitrate, it will so far not 

 only have no food value, but it may be positively injuri- 

 ous. It may be added that, other things being equal, 

 the higher the percentage of nitrogen in roots the lower, 

 as a rule, will be the proportion of it as albuminoids, 

 and the higher that as amides and as nitrate, etc. 

 Further in direct experiments at Rothamsted with sheep 

 feeding on roots alone, it was found that while the 

 animals even gained in weight on ripe roots, low in 

 nitrogen, they actually lost on roots that were less ripe, 

 high in nitrogen, and doubtless containing a larger pro- 

 portion of their nitrogen as non-albuminoid compounds." 



It is true that nitrates by themselves have not a very noxious 

 effect on animals as it requires about 2.5 g. of potassium nitrate for 

 I kilo of body-weight of an animal to bring on death, but there 



(1) Birthelol found that the amount of nitrates may vary from o to 15 % in potato, 

 from o to 2.8 % o in wheat, from o to 15 % in Amaranius. (Chem Centralbl. 1SS4, 

 639)- 



The amount in turnips and beets was found to vary between 0.5 -3.5 % of the dry 

 matter {Ebermayer, Physiologische Chemie der rflanzen). 



