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XIV. On the Temperature of Man. 

 By John Davy, M.D., F.R.S.L. 8f E,, Inspector-General of Army Hospitals. 



Received May 8, — Read June 19, 1845. 



It has been too generally taken for granted that the temperature of man in health, 

 as measured by a thermometer placed under the tongue, is a constant one. I have 

 endeavoured to prove from the results of observations, that this is not strictly correct ; 

 that when not disturbed by disease it is subject to variation, to rise and fall under 

 certain influences, especially of heat and cold, rest and exercise*. 



In the present communication I propose to submit to the Royal Society some 

 further observations on the same subject, made with an instrument better adapted 

 for the inquiry than the medical thermometer commonly used, and which has afforded 

 results of a precise and satisfactory kind. 



The thermometer I have employed is a bent one, about twelve inches and a half long, 

 its bulb about an inch long, and, where widest, half an inch thick ; its curvature about 

 three and a half inches from the bulb, and its stem, to which the scale is attached, 

 nearly at right angles to the bulb, so that when inserted under the tongue, the ob- 

 server has no difficulty in distinguishing accurately the degrees himself, whether near- 

 sighted or the contrary; in the latter instance using merely a common magnifying 

 glass. Each degree of the scale is a little more than half an inch ('6 inch), and is 

 divided into ten parts ; and each of these parts is sufficiently large to admit of sub- 

 division by the eye. 



It may be right to premise a few words regarding the manner of observing with 

 this instrument ; and to notice some precautions which it is necessary to take to 

 avoid error. 



First, as to the placing of the thermometer: it is requisite that the bulb should be 

 introduced under the tongue, and as far back as possible ; and that whilst in the 

 mouth, respiration should be carried on entirely through the nostrils. If the ther- 

 mometer is placed in the side of the mouth, between the teeth and the cheek, the 

 temperature indicated is from three-tenths to one-tenth of a degree less, according to 

 the degree of coldness of the atmosphere. 



Next, as to time : it is necessary that the thermometer remain in the mouth many 

 minutes, till the observer is sure that the maximum height is attained. If the mouth 

 has been kept closed for a quarter of an hour previously, a shorter time is required, 

 than if allowed to be open and the passage of respiration. This is well shown by 

 trials with the thermometer raised a few degrees above the temperature of the mouth 



* Researches, Physiological and Anatomical, vol. i. p. 162 ; and Philosophical Transactions for 1844, p. 61. 

 MDCCCXLV. 2 U 



