under Various Electrical Conditions. 
141 
The living material having been enclosed in the chamber, the air- 
stream was drawn through the apparatus for a definite period — half an 
hour, an hour, or two hours, — depending upon the time required for the 
evolution of a measurable quantity of carbon dioxide. 
The stream was then diverted through a second Pettenkofer tube for 
a similar period, and so on until the required number of determinations had 
been made. By means of two seven-way pieces of glass tubing and six 
Pettenkofer tubes, each capable of being closed separately by pinchcocks 
and rubber connexions, this transference of the air-stream from one tube to 
another was rendered rapid and easy. 
The titration was carried out with standard oxalic acid solution. The 
baryta solution in the Pettenkofer was quickly transferred to a flask of 
about 125 c.c. capacity, so as to introduce as little atmospheric carbon 
dioxide as possible, corked and shaken. 
After a few minutes the precipitate had settled and 10 c.c. of the clear 
supernatant liquid were pipetted off into another flask and titrated from the 
acid burette, using phenolphthalein as indicator. 
The standard solutions were kept in large bottles provided with 
siphoning tubes, which were attached to side tubes in the respective burettes. 
Air was admitted, both to stock bottles and burettes, only after passage 
through tubes containing sticks of potash, so as to prevent access of atmo- 
spheric carbon dioxide. The baryta solution contained approximately 
9 grm. per litre, and was standardized by the oxalic acid solution, which 
was made up to 1*432 grm. of the crystallized acid per litre, 1 c.c. of this 
solution being equivalent to 0-0005 grm. carbon dioxide. This, coupled with 
the fact that the volume of baryta in each Pettenkofer tube was exactly 
100 c.c., simplified the calculation of results. 
Before entering upon the experiments under various electrical con- 
ditions, extensive control trials were carried out, in order to ascertain to 
what extent variations of carbon dioxide output might occur under the 
conditions of the experiment, apart from the influence of the electric 
current. 
Determinations of the carbon dioxide evolved were made every half- 
hour from the moment the living material was introduced into the chamber, 
and continued without intermission for as many as six hours, the material 
being unelectrified the whole time. The figures obtained were then plotted 
against time, and a curve was thus obtained which gave an indication of 
the process of the respiratory function. During the investigation, as will 
be seen, it was found necessary to employ various types of respiration- 
chambers, and with each type a series of these control experiments was 
carried out. 
