260 DR SUTHERLAND SIMPSON ON 
raised, and still, as a result of the exercise, it rose higher. During the walk the mouth 
was kept closed except on November 1, and that is the only occasion on which the 
temperature fell. The outside temperature has much to do with this, of course, and it 
is probable that in many of LriypHaRp’s experiments it was below zero. He does not 
give the air temperatures, but when his observations were made indoors it is not likely 
that the atmosphere was as cold as that to which I was exposed in my walks on 
November 1 and 3, when the temperature was only one or two degrees above the 
freezing-point, and a cold wind blowing at the same time. LrinpH#arp found in his own 
case and in other members of the crew that as a rule the mouth temperature did not 
rise during work. ‘‘On working indoors it was almost constant; on working in the 
open air it always falls.” The only explanation of the difference in the results is that — 
it depends on individual peculiarities, or rather, on mouth peculiarities. The thinner 
the walls of the buccal chamber the greater and more rapid will be the dissipation of 
heat and the more difficult will it be to raise the temperature. The relative vascularity 
of the parts is probably also of importance. 
In my case the temperature of the axilla also rose during the walk, or at any rate — 
did not fall. On November 1 and 3 it remained constant. 
VII. Summary. 
To determine whether the diurnal variation in body temperature is due to the 
combined effects of the various influences which are known to act upon it, such as 
muscular exercise, the ingestion of food, sleep, etc., or is present independently of 
these, the daily routine of the individual who is the subject of the experiment may 
be reversed artificially by causing him to work during the night and rest and sleep 
during the day, or it may be modified in another way, viz. by rapidly changing his 
longitude in a journey from west to east, or vice versa. If the temperature of the body 
is dependent on the influences mentioned, then a total reversal of the daily routine, 
or any modification of it, should produce a one change in the diurnal 
temperature curve. | 
On a voyage from Ithaca, in the western part of New York State, to Edinburgh, 
during six weeks’ residence in Scotland, and again on the return journey from Edinburgh — 
to Winnipeg, continuous three-hourly observations (and hourly from 6 a.m. to 9 a.m.) 
were made by the writer on his own temperature (rectum, mouth and axilla), except 
between midnight and 6 a.m., with a view to ascertain whether the temperature rhythm 
obeyed local (ship’s) time or Ithaca time. To get the Ithaca rhythm as a control, 
observations were made in that city for one week before the journey began. If a 
temperature periodicity were fixed in the body independently of external conditions, — 
then the curve should correspond to Ithaca time and not to local time as he travelled — 
from west to east, or vice versa. For example, since Edinburgh local time is five hours — 
in advance of Ithaca local time, the morning rise which began at 7 a.m. in Ithaca 
