remarkable Effects of a Shipwreck. 223 
having been made in contact with the body, I will not deny 
that there is some foundation for the remark ; and the cases, 
it must be allowed, are by no means exactly parallel between 
immersion in an open vessel, however large, and immersion in 
the sea, where the constant undulation may be presumed to 
occasion a continual change in the surrounding fluid. But 
whatever allowance may be made for the circumstance men- 
tioned, I am persuaded that the difference between the density 
of air and water being considered, it is not sufficient to ex-* 
plain the loss of heat in the instance alluded to. The changes 
of temperature in the living body are governed by laws pe- 
culiar to itself. I have found, in certain diseases, greater and 
suddener variations than any mentioned, from applications of 
cold very gentle in degree, and momentary in duration. 
I11 his masterly “ Experiments and Observations on Animals 
producing Heat/' Mr. Hunter has objected to taking the 
heat of the human body by introducing the bulb of the ther- 
mometer into the mouth, because it may be affected by the 
cold air in breathing. The objection is well founded if the 
bulb be placed on the upper surface of the tongue, but if it be 
under it and the lips shut, the effects of respiration may be 
disregarded, as I have found from many hundred experiments. 
The heat may be observed in this way with ease and cer- 
tainty, by employing thermometers curved at that end to 
which the bulb is affixed (the bulb being introduced at the 
corner of the mouth), some of which have been made for me 
by Mr. Ramsden according to a form given, as well as others 
on Mr. Hunter’s plan. From repeated trials it appears to 
me, that when the usual clothing is on, the heat of the living 
body may be taken, with nearly the same result and equal 
Gg2 
