656 



ANIMAL HEAT. 



on the magnetic needle, causes it to deviate by 

 a certain number of degrees, which conse- 

 quently become indices of the temperature of 

 the point of the needle, and therefore of the 

 medium in which it is placed. The multiplier 

 ought to be so sensitive as to show a deviation 

 of one degree of the magnetic needle for each 

 one-tenth of a degree of temperature as mea- 

 sured by the centigrade scale, an amount of 

 temperature made sensible by the union of the 

 two ends of the wire which forms its circuit 

 with an iron wire soldered by its ends. 



So much for the general principle upon 

 which and by which the inquiries of Messrs. 

 Becquerel arid Breschet were conducted. As 

 to all the precautions necessary to render re- 

 searches of the kind fruitful, as these are nume- 

 rous, we beg to refer for an account of them to 

 the memoir of the authors themselves. 



Difference of temperature according to the 

 depth. By the means contrived by Becquerel 

 and Breschet the temperature of the calf of the 

 leg at the depth of four centimetres from the 

 surface was found to be 36,75 (about 98 F.), 

 and at one centimetre 34,50 (about 94 F.), 

 a difference of 2,25 (4 F.). In the chest the 

 temperature at the depth of the pectoralis 

 major, compared with that of the superficial 

 cellular tissue at the depth of one centimetre, 

 showed a corresponding difference; the deeper 

 parts were 2,25 (about 4 F.) higher than the 

 tnore superficial. In seven experiments made 

 on the arm the mean difference of temperature 

 between the deeper strata of the biceps and the 

 superficial cellular tissue over the same muscle 

 amounted to 1,59 c. in favour of the deeper 

 parts. 



The next point of inquiry was to know whether 

 it was enough to penetrate to the depth of three 

 or four centimetres into the trunk and limbs to 

 attain the points of highest temperature in 

 these parts. With this view we have compared 

 the observations made by the authors mention- 

 ed, in the same individual, with regard to the 

 temperature of the mouth and of the biceps 

 muscle, and we find that the mean temperature 

 of the mouth was 36,89, that of the biceps 

 36,88, (about 98 F.), a result which may be 

 called identical with the former. The mean of 

 seven other experiments, however, shows the 

 relation of 36,89 c. for the rnouth, of 36, 75 c. 

 for the biceps ; the difference here is evidently 

 in favour of the mouth. It were to be wished 

 that inquiries in this direction were multiplied 

 in order that absolute certainty may yet be 

 attained. 



In the preceding experiments, in penetrating 

 to different depths, the nature of the tissues at- 

 tained also differs, a circumstance which must 

 tend to complicate the results ; for it is possi- 

 ble that the nature of the tissue may have some 

 influence on the evolution of heat. This is 

 even an inference which we should deduce 

 from the principles already established, were it 

 merely in consideration of the different quanti- 

 ties of blood they contain. And this conclu- 

 sion is even confirmed by the experiments of 

 the parties mentioned ; for on compressing the 

 humeral artery strongly, the motion of the nee- 



dle immediately announced a fall of tempera- 

 ture to the extent of several tenths of a degree. 

 This experiment is interesting from the rapidity 

 and precision of the effect. There are other 

 cases well known by which we are led to a 

 corresponding conclusion ; but nowhere else is 

 the fact seen in so simple a guise, or in so ma- 

 nifest a relation of cause and effect. In opera- 

 tions for aneurism, indeed, and other cases re- 

 quiring the ligature of a large artery, the tem- 

 perature of the parts supplied by the vessel 

 tied falls so low as to require to be supported 

 by artificial warmth ; but then a severe and 

 bloody operation has been performed by which 

 the conditions are complicated. In the expe- 

 riment mentioned, on the contrary, nothing 

 occurs to disturb the state of the economy ; the 

 effect instantly follows the cause, and its 

 amount is even at the same moment ascer- 

 tained. 



Seeing, then, that in the same tissue the freer 

 or more interrupted access of arterial blood 

 causes the temperature to vary, it is fair to infer 

 that the relative freedom of access or quantity 

 of this fluid which circulates through other 

 tissues should have an influence upon their 

 temperature ; in other words, that tissues differ 

 in their power of producing heat according to 

 the quantity of blood which circulates through 

 them. We can scarcely doubt, therefore, but 

 that the differences of temperature observed be- 

 tween the deeper and more superficial parts are 

 complicated by the mere fact of difference of 

 distance from the surface, and also by the cir- 

 cumstance of difference of tissue. The super- 

 ficial layer in the preceding experiments was 

 cellular membrane ; the deeper layer was mus- 

 cular. But the muscles receive a much larger 

 quantity of blood than the cellular membrane, 

 and their temperature, from this circumstance 

 alone, ought to be higher.* 



* [Messrs. Becquerel and Breschet, in a memoir 

 lately read before the Royal Academy of Sciences, 

 (Ann. des Sciences Nat. Mai 1838.) entitled, 

 " Further Observations on the Temperature of the 

 Tissues of the body of Man and the lower Animals, 

 as ascertained by means of thermo-electric effects," 

 have made a few additional observations which de- 

 serve quotation in this place. The temperature of 

 the mouth being used as the standard of compari- 

 son, the temperature of the biceps muscle was 

 found to be but 36, 20 c., instead of 36, 60, 

 which was the term derived from previous experi- 

 ments, and to fall short of the temperature of the 

 mouth by as many as 4 c. (above 7 F.) 



In making experiments upon the influence of 

 the temperature of surrounding media upon that of 

 the tissues, Messrs. Becquerel and Breschet intro- 

 duced the needles of their thermo-electrical appara- 

 tus into the biceps muscles of two young and 

 healthy individuals, the air at the time marking 

 16 c. (61F. ). The magnetic needle did not deviate 

 in the least ; so that the two muscles possessed 

 precisely the same temperature. One of the arms 

 was now immersed for a quarter of an hour in water 

 of the temperature successively of 10, 8, 6 Q , and 

 Q c. (50, 47, 43, and 32 F.). The deviation of 

 the needle did not amount to more than two degrees 

 of its scale in favour of the muscle of the arm which 

 was not plunged into the water. The partial cold 

 bath, consequently, had only caused a depression 

 of temperature to the extent of about one-fifth of a 

 degree c. The arm being now plunged into water 



