678 



ANIMAL HEAT. 



unless suitably treated, dies in the cold stage of 

 the second or third paroxysm ; sometimes he 

 will even perish in the first. 



It is easy to produce at will the essential 

 symptoms of these affections even in their most 

 formidable shapes, in animals in a state of 

 health. All the young birds, for example, 

 belonging to the group of those which at their 

 birth have the weaker calorific powers, can be 

 made to exhibit the phenomena in question. If, 

 at the period of their exclusion or shortly after 

 this, they be taken out of the nest, we have 

 seen that they lose heat rapidly even in the 

 summer season; and we perceive that any 

 reaction of which they are capable by the 

 acceleration of their respiratory and circulatory 

 motions avails them nothing ; their tempera- 

 ture sinks in spite of this, till all reaction 

 ceases by the increasing and now benumbing 

 influence of the cold, so that they speedily 

 perish. In these two extreme cases of dimin- 

 ished production of heat, there is similarity in 

 the symptoms which ensue, witli this difference, 

 that in the algid intermittent there is lesion or a 

 morbid state of the calorific faculty ; whilst in 

 the other case the scanty production of heat is 

 a normal condition in relation with ihe age of 

 the subject. In the first, the constitution is 

 seriously altered ; it must be restored or other- 

 wise the individual dies; in the second, there 

 is no alteration of any kind ; the individual 

 only requires to be placed in circumstances 

 favourable to the normal manifestation of the 

 function to be restored. In the one the 

 lesion is so great that there is no resource in 

 nature abandoned to her own efforts ; art must 

 interfere. In the other, nature provides against 

 the scanty production of caloric in giving to 

 parents the instinct to warm their young by the 

 heat of their own bodies, &c. 



We have seen that cold, when not of too 

 great intensity, tended to strengthen the body 

 by increasing the faculty of producing heat ; 

 and farther, that with the progressive rise of 

 the temperature in spring and summer the 

 energy of this faculty diminished. This is 

 what takes place with regard to those constitu- 

 tions that are in the most favourable relation 

 with the climate. Let us now examine the 

 nature of those constitutions that do not adapt 

 themselves thoroughly to the changes of the 

 seasons, and see what the consequences are with 

 regard to them. Let us begin with the rela- 

 tion of these to the cold season of the year. 

 It might be presumed priori that those con- 

 stitutions that have a very limited capacity of 

 engendering heat will not accommodate them- 

 selves well to the cold of winter. Their 

 limited powers of producing heat will not ena- 

 ble them to repair the continually increasing 

 loss of it arising from the depression of the 

 external temperature. They consequently suffer 

 in a greater or less degree from cold, perhaps 

 not to any great extent in the first instance, 

 as we shall have occasion to explain by-and- 

 by, but still in some measure ; and there are 

 certain degrees of uneasiness and inconvenience 

 that may be regarded as being still within the 



limits of health. There is even a certain, and 

 that a pretty wide latitude in which the body 

 may vary without trespassing on the line of 

 disease. The uneasiness may only be ex- 

 perienced from time to time, and not even be 

 always very manifestly referable to its proper 

 cause. In other words the sensation may be 

 something quite different from that ordinarily 

 induced by cold; just as it sometimes happens 

 that among weak constitutions the necessity of 

 taking food is not always proclaimed by the 

 feeling of hunger, but occasionally by some 

 other distressing or painful sensation, with re- 

 gard to the true nature of which experience 

 alone can enlighten us. In such a low state of 

 the calorific power, the Faculty seems to lose 

 strength still further, owing to the simple per- 

 sistence of the same degree of cold, and still 

 more from the ulterior depression of the tem- 

 perature, in the manner we have seen when 

 speaking of hybernating animals. This dimi- 

 nution in the temperature of the air sometimes 

 occasions among weakly subjects morbid re- 

 action, the principal features of which have 

 already been explained. From all that pre- 

 cedes, the constitutions that will be the most apt 

 to suffer from exposure to cold will be those of 

 the earliest times of life observed in man and 

 the warm-blooded tribes generally, since it is 

 at this epoch that they produce the least heat ; 

 and as a corollary from this, we should infer 

 that the mortality in early life ought to be 

 greater during the winter season in this and 

 other countries similarly circumstanced. It 

 became a matter of peculiar interest to verify 

 this inference from the experiments and 

 reasonings of which we have just rendered an 

 account. Messrs. Villerme and Milne Edwards 

 accordingly undertook the necessary inquiries, 

 entering upon extensive statistical researches 

 with reference to the mortality of children in 

 the different seasons of the year in France, and 

 found that the mortality of infants from their birth 

 to the age of three months was generally the 

 greatest in those departments of which the 

 winters were the most severe. For a similar 

 reason, the natives of very warm climates who 

 visit countries whose winters are excessively 

 cold, run great risks of not being able to pro- 

 duce heat enough to compensate the loss they 

 sustain from exposure to the low atmospheric 

 changes, and thus of becoming obnoxious to 

 disease and death in consequence. Those that 

 have elasticity enough of constitution to meet 

 this unwonted demand upon their calorific 

 powers, experience an increase in the energy of 

 the functions upon which the production of heat 

 depends, by which they are brought into har- 

 mony with the climate. Others who are less 

 robustly constituted complain loudly of the 

 cold, languish, and finally perish if they do not 

 find means of escaping from the destructive 

 tendency of the cold. 



What happens, in as far as these different con- 

 stitutions are concerned, when the change of 

 season is the opposite of that we have just dis- 

 cussed ? when the progress is from the colder 

 to the hotter period of the year ? The constitu- 



