CONSERVATIVE DESIGN OF ORGANIC DISEASE. 169 



ing organisms implied by the existence of a liability to be fatally in- 

 jured by it, may be found in the fact that Nature has amply provided 

 for maintaining all very young animals at an elevated temperature, 

 and protecting them from external cold. Note, first, how animals 

 usually breed during the seasons of spring and summer; and observe, 

 further, how the bird feathers her nest for the reception of her young, 

 and shelters them under her wings, at the same time imparting heat 

 by the contact of her own warm body. Rabbits and other animals 

 tear off the fur from their own skins in order to provide a warm bed 

 for the young while the parent is away in search of food. Frequently, 

 too, animals are born in broods, or litters, especially those that are 

 nearly nude at birth, and incapable of generating heat by exercise, and 

 thus warmth is generated, or at least maintained, by the crowding to- 

 gether of a number of individuals in a small space. 



Whether the liability, on the part of young animals, to be inju- 

 riously influenced by cold, is owing to their vital forces being so taken 

 up with the process of growth as to leave a smaller surplus of vitality 

 to resist the chemical agency of a diminished temperature, or whether 

 it is that the lack of muscular exercise in them prevents the develop- 

 ment of heat, we may not be able to determine ; but this question is 

 immaterial so far as the fact itself is concerned, that cold acts injuri- 

 ously. It seems not improbable that the liability to be unusually af- 

 fected by cold may depend upon rapidity of organic change. Thus 

 those organs are most readily afiected whose evolution is in most rapid 

 progress ; hence the digestive organs of the child and its pulmonary 

 tissues are more apt to suffer from a depressed temperature than its 

 reproductive organs ; the former are undergoing rapid development^ 

 the latter are in a state of almost complete quiescence. Similarly the 

 increased rate of tissue-change incident to violent activity of function 

 appears to increase the susceptibility to cold ; thus any one who has 

 unusually exercised certain muscles will, after exposure, find those 

 muscles become painful, " stiff," tender, and inflamed, Avhile the re- 

 maining muscles of the body will have escaped any such manifesta- 

 tions. Buds that have withstood the severest cold of winter are often 

 killed by the late but more moderate frosts of spring, because at this 

 latter period they are in a state of more rapid tissue-change. The ^^^^ 

 of the fowl will bear a considerable degree of cold withoiit losing its 

 vitality so long as its evolutionary processes are at a stand-still ; but, 

 when the rapid changes of structure incident to embryonic develop- 

 ment have been set up, exposure even to the ordinary atmospheric 

 temperature of spring and summer, if at all prolonged, is suflicient to 

 destroy its life. 



The greatest security against injury, therefore, from exjiosure to 

 cold, would seem to be (comparative) structural stability organic rest. 

 But, in whatever manner to be explained, the fact remains that pro- 

 cesses of physiological development may be disastrously embarrassed 



