THE PHYSIOLOGY OF DEEP-SEA LIFE. 295 
mouth of the flask by a close-fitting india -rubber stopper. 
The tube of the bulb has a lateral opening from an ingenious 
slide- valve between the bulb 
and the flask. To the upper 
part of the bulb is attached a 
gas-tube with a double-ended 
pipette, in which a vacuum is 
formed by boiling out distilled 
water from the bulb, closing the 
upper end of ‘the gas-tube, and 
then making a connection with 
the flask, which under the re- 
lieved pressure will allow the 
gas contained in the sea-water 
to find its way into the gas- 
tube. This is then sealed at 
the other extremity, and the 
contents analyzed on shore. 
Dr. Jacobsen concluded from 
his analyses that the percent- 
age of oxygen in sea-water was 
practically invariable, the low- 
est and highest percentages be- 
ing 33.64 and 34.14. While iii 
this is undoubtedly true for lim- Fg. 198. — Bunsen's apparatus, modified 
b by Jacobsen and Behrens. 
ited areas, the analyses by Dr. 
J. Y. Buchanan of the “Challenger” show that, under varied 
conditions of temperature, there was a somewhat wider range, 
— between 33 and 35 per cent, in round numbers. The pro- 
portion of oxygen being greatest on the surface, it begins at 
once to diminish rapidly till it reaches more slowly a minimum, 
at a depth of 300 fathoms; and below this depth, its percent- 
age remains constant. This does not quite agree with Dittmar’s 
results stated further on. 
The carbonic acid in the water was determined directly by dis- 
tilling in a current of air conveying the gas, and collecting the 
steam and carbonic acid in a vessel charged with baryta water. 
By adding to the water to be tested a measured quantity of acid 
