i68 THE POPULAR SCIENCE MONTHLY. 



be found to be the same both in physiological and pathological develop- 

 ment. 



Most prominent among the conditions necessary to secure the nor- 

 mal progress of physiological development is warmth; and nothing 

 more decidely interferes with it, or more quickly arrests it, than ex- 

 posure to cold. In fact, an elevated temperature is the initial power 

 the first mover of the developmental process in all organisms, vege- 

 table as well as animal. It is solar heat that forces the seed to germi- 

 nate, the plant to bud, and the flower to bloom. Without warmth the 

 fecundated egg of the oviparous animal would ever remain an inert 

 mass ; hence the snake deposits her germs in a dunghill of rotting 

 vegetable matter where they may be warmed by the heat of fermen- 

 tation. The ostrich intrusts her egg almost entirely to the sun-baked 

 sand of the African desert ; and birds in general incubate for days or 

 weeks to supply the necessary heat for securing the development of 

 their eggs. Fish inhabiting waters that are deep and cold, seek shal- 

 lower and warmer streams in which to deposit their spawn. The dif- 

 ference between the warm and the cold seasons of the year, as regards 

 the prevalence of reproduction, in both animals and plants, is familiar 

 to every one. 



But, besides heat being the primiim mobile of normal evolution, it 

 is equally necessary to maintain it when already begun. Exposure to 

 cold is fatal. The shivering of young animals their great liability to 

 become chilled on exposure -to a dejiressed temperature has been 

 observed by every one ; and in the breeding of domestic animals, as in 

 the cultivatiou of j)lants, there is probably no more potent source of 

 mortality thaninsufiicient warmth ; and, further, this mortality is found 

 to be more prevalent during unusually cold seasons. Now, the young 

 of our own species form no exception to this rule ; they, too, are liable 

 to suiFer a fatal arrest of pliysiological development on being exposed 

 to cold. Thus, in a statistical inquiry as to the average number of 

 deaths at different seasons, and at diffei'ent ages, from a table pre- 

 pared by M. Quetelet, of Brussels, it appears that, during the first 

 month of infant life, the external temperature has a very marked in- 

 fluence ; for the average mortality during each of the three summer 

 months being 80, that of January is nearly 140, and the average of 

 February and March 125. This is confirmed by the result obtained by 

 MM. Villerme and Milne-Edwards in their researches on the mortality 

 of the children conveyed to the foundling hospitals in the different 

 towns in France ; for they not only ascertained that the mortality is 

 much the greatest during the first three months in the year, but also 

 that it varies in different parts of the kingdom according to the rela- 

 tive severity of the winter.^ 



Additional proof of the disastrous influence of cold in early life, 

 and, by-the-way, an explanation of the apparent natural defect in grow- 



' See Carpenter's " Human Physiology," American edition of 1856, pp. 419, 420. 



