ANIMAL HEAT. 



663 



direction we are considering. We have seen 

 that with a decrease in the size of adult Mam- 

 malia the circulatory and respiratory motions 

 were progressively accelerated, and that by this 

 means the disadvantages as regards cooling in 

 consequence of a smaller relative size of the 

 body, are in some measure compensated, some- 

 times, indeed, we have seen the balance in- 

 clined the other way, and the greater rapidity 

 of the motions more than compensate for the 

 diminished size of the body. Great rapidity 

 of the respiratory and circulatory motions may 

 co-exist with other organic conditions having 

 an opposite tendency as regards temperature ; 

 and, according to the relations of these, and 

 as the one or the other predominates, we may 

 have two different states of temperature in 

 early life. This proposition is even made ap- 

 parent when we compare the constitution in 

 early youth and in adult age. In early life the 

 celerity of the motions has led to the belief 

 that all the functions of nutrition were pecu- 

 liarly active. But strength or energy is not 

 always an accompaniment of simple celerity ; 

 on the contrary rapidity is generally indicative 

 of absence of power. It is quite true that in 

 early life not only are circulation and respira- 

 tion, but digestion, assimilation, and growth 

 likewise, much more rapid than in the adult 

 state. But does it follow from this that the 

 materials of the blood are elaborated in the 

 same degree of perfection, or that the products 

 of the action and contact of this fluid, the 

 various tissues, &c. of the body, are all as com- 

 pletely formed ? Everything conduces to make 

 us believe that the reverse is the case. If on 

 the one hand rapidity of movement be a cha- 

 racter of early life, weakness is a feature still 

 more manifest. If the nervous system there- 

 fore, although acting rapidly, is less energetic, 

 in the same proportion there may be an age at 

 which the influence of this weakness on the 

 production of heat may be manifest. And, as 

 the weakness is greater as the being is younger, 

 it is in the very earliest periods of independent 

 existence that this relation must be inves- 

 tigated. Now such a relationship does actually 

 exist, although an opinion to the contrary had 

 always been entertained until direct experi- 

 ments settled the question definitively. These 

 experiments were performed by the writer, and 

 a summary of them is here given. If the 

 temperature of new-born puppies lying beside 

 their mother be taken, it will be found from 

 one to three degrees inferior to that of the 

 parent. The same thing obtains in regard to 

 the young of the rat, the rabbit, the guinea-pig, 

 &c. and is probably universal among the Mam- 

 malia. Among Birds the same circumstance 

 presents itself in a still more marked degree. 

 If they be taken out of the nest in the first 

 week or even fortnight of their existence, the 

 difference of temperature extends to from 2 

 to 5 c. between the young and the parents. 

 The fact has been ascertained in regard to the 

 sparrow, the swallow, the martin, the sparrow- 

 hawk, the magpie, the thrush, the starling, 

 &c. &c., and is probably, as among Mammalia, 

 universal. Whence we may conclude that the 



phenomenon is general as regards warrrt-blooded 

 animals. We might have taken it for granted 

 that man was comprised within the category, 

 but it is just as well to have the assurance that 

 he forms no exception to the law, that he has 

 no peculiar privilege in this respect. To have 

 a precise term of comparison, the temperature 

 of twenty adults was taken at the same time, 

 the thermometer being applied in the axilla. 

 The temperature of these twenty persons varied 

 between 35, 5 and 37 c. (96 and 99 F.) ; 

 the mean term was therefore 36, 12 (97 F.). 

 The temperature of ten infants varying from a 

 few hours to two days in age, ascertained in 

 the same manner, varied between 34 and 35 5 

 c. (93, 5 and 96 F.). The mean was there- 

 fore 34, 75 c. (about 94, 5 F.). There was 

 consequently a difference of nearly two degrees 

 between the temperature of the adult and of 

 the newly born babes. Man is therefore proved 

 to be subjected to the same law here as ani- 

 mals having warm blood in general, the young 

 of which, so far as they have been examined, 

 and we may presume universally, are inferior 

 in temperature to their parents. 



There are, therefore, two periods in youth at 

 which the bodily temperature differs from that 

 of the adult age. These may be distinguished 

 as the first and second periods of infancy or 

 youth. The first extends from birth to an in- 

 definite period, but which is nearer or more 

 remote from the period of birth in different 

 cases. The second is included between the 

 fourth and the fourteenth year ; the limits can- 

 not be more accurately determined. In the 

 first the temperature is lower than in adult age, 

 in the second it is higher. The differences of 

 temperature in the first age of infancy, and the 

 adult age, although very sensible and impor- 

 tant as regards the economy, are indices of a 

 difference incomparably greater than their 

 numerical indication might be taken to imply. 

 In fact, if the manner of observing be altered, 

 results of so extraordinary a character are come 

 to as to surpass all expectation. To deve- 

 lope these the temperature of the newly bom 

 being must not be taken only when it is in 

 contact with its mother. If, after having as- 

 certained the temperature of a puppy in this 

 position, it be removed from the mother and 

 kept isolated, the temperature will be found to 

 fall rapidly ; and this phenomenon takes place 

 not only when the air is cold, but when it is 

 mild. The phenomenon does not commence 

 after a term ; it is apparent from the moment 

 the separation takes place, and is very sensi- 

 ble after the lapse of a few minutes. The fol- 

 lowing is the rate of cooling of a puppy twenty- 

 four hours old, the external temperature being 

 13 c. (about 55, 5 F.), taken at intervals of 

 ten minutes; the series of course represents 

 the successive losses of temperature in the 

 course of the small intervals of time indicated : 

 temperature in commencing the observations 

 36, 87 c.; the declensions in temperature at 

 intervals of ten minutes successively, 0, 63, 

 1, 12, 1,38, 1,25, 1,29, 0,87, 1,63, 

 0, 25, 1, 0; in thirty- five minutes the tem- 

 perature declined fart tr 1,25; in thirty-five 



