122 Transactions. 
are required in very small quantities, such as fluorine and iodine. Nothing 
is known of the exact need for the former, which must be required only 
in very small amounts, and the latter has been administered to a sick beast 
without effecting any improvement. Bush sickness occurs in coastal dis- 
tricts where sulphur is not likely to be wanting. Thus by a process of 
elimination one naturally arrives at iron as being the deficient element. 
Of the igneous rocks, the rhyolites, from which the bush-sick soils are 
derived, are among those rocks which contain least iron. The rhyolitic 
froth—pumice—which forms the soils, had no doubt been leached before 
being redistributed by a series of explosions in geological time, long after 
its formation in the volcano. This redistribution took place, according to 
Thomas,* not long before the Maori came to New Zealand, which would be 
probably about a thousand years ago. 
The amounts of iron extracted by hydrochloric acid from these pumice 
soils is of the order of 1 per cent., but the amount extracted in Dyer's 1-per- 
cent. citric-acid method for “ available plant-food " gives about 0-03 to 
0-07 per cent. iron, whereas on non-bus -sick pumice soils the amount rises 
from 0-07 to 0-1 per cent., and on non-pumice soils it may rise to 0-3 per 
cent. These amounts for iron, compared with the standard amounts 
days, but a calf takes forty-seven, a colt sixty, and a human child 180 days. 
Human milk and mares’ mi i i 
* A. Р. W. Tuomas, Report on ће Eruption of Tarawera and Rotomahana, N Z., 
Wellington, 1888, p. 19. 
