DEVELOPMENT. 35 



lowered condition of nutrition is indicated by the 

 lessened amount of movement. The dormouse 

 when hybernating has its nutrition lessened, owing 

 to the little food it takes ; its feeble circulation, 

 its lowered temperature, and the absence of move- 

 ments in the limbs are the expressions of its 

 lessened nerve-muscular energy. 



Development is a very interesting and important 

 study. It is expressed in various modes. In the 

 newly born infant we observe certain conditions 

 indicated by its weight, form, proportions, etc., i.e. 

 certain conditions of its body ; we also observe 

 certain functions, movements, reflex actions, etc. 

 These are the expressions of its condition. In the 

 adult the weight, form, proportions, and the move- 

 ments and reflexes, are different from those of the 

 infant, and this difference is an expression of the 

 evolution of the individual. After comparing many 

 infants with many adults, and observing the de- 

 velopment of infants into adults, we find that a more 

 or less regular series of similar changes occurs in the 

 body, and in its functions, as development advances 

 from infancy to adult age. This more or less 

 regular series of changes in the body, and in its 

 functions, is the expression of the development, and, 

 in any case, before we can give a full historical 

 account of the development, we must observe all 

 modes of its expression. The life-history of an 

 individual animal is in part the history of its de- 

 velopment ; it includes the description of the body 

 of the individual at every period of its existence, 

 together with all the influences afferent to it, and 



