APPARATUS A*D MffTTODS 



The oxygen free *atar *«• obtained fro* the water boiling Apparatus 



in the vivarium at the University of Illinois which has besn described by 



Shelford (193 This apparatus consists primarily of a boiler ir. v L*k the 



vater is boiled by <*e*ns of bigfe presaura ateam un.il practically all of the 



gasss are driven out and from ahioh it passes into a tank covered by a hood 



whs re boiling is continued until the water is freed of gases. The flow cf 



water into th? boiler is regulated by a float cork. The oxygen free vater is 



withdrawn from the hooded tank, passes through cooling pipae in the ruo» below 



where it is used. As It cuasea from the pipes it contains no oxygen (Winkler 



method) Ml ie strongly alkaline, due to the C0~ h-ving been expelled by long 



boiling and fetish of the bicarbonate having been converted into carbonates. A 



series of different oonoentr^tiono cf oxygen was obtained l^j syphoning the 



water through a series of half -gallon mason jars (fig.l) through alternate ones 



cf which air *as bubbled. Ths water from the last of these was siphoned into 



a fivs-inch beaker so that the level of water ir ths Jars co ild not fall below 



five inches. It was found by titration that the Oi concentration varied greatly 



in the different p».rts of a Jar through which s. stream of air wae passing, but 



was relatively constant except at the surface in a Jar through which the water 



was be in;: siphoned fc».t no air was passing; consequently the jars containing 



the exparlsiental anlmale were alternated with those which were being aerated, 



with the result that such oxperi •»■.■•• nt j.ar contained a little ora O3 than the 



one preceding. 



The flos of air through the water was regulated by passing it 



larvfegjl capillary tubes drawn to a fins point and the air pressure was kept 



relatively constant by means of a mercury manometer made by bending a D at one 



