488 PEDIATRICS 



during the course of growth a continual change in their relative 

 size, is shown in the table prepared at my suggestion by Oppen- 

 heimer; it displays the weight of the organs at the different years 

 of life (compared with the weight of the organs in the new-born). 

 The consideration of these relationships, together with the obser- 

 vations already mentioned, shows that the growth of the individual 

 organs does not occur simultaneously, but with varying intensity, so 

 to speak by jerks, and that the order is caused by the greater or lesser 

 importance of the developing organs' for the preservation or protection 

 of the infantile life. This I call the third rule of growth. 



The life of the child in utero and at the beginning of its extra- 

 uterine existence is so purely vegetative as to make Plato consider 

 seriously the question whether the new-born is actually to be con- 

 sidered as a human being. But just as the intellectual life is bound 

 up with the function and development of the brain, so is the vegeta- 

 tive life with the function and development of the organs serving 

 metabolic ends. The most important of these are the circulatory 

 system, the liver, kidneys, and lymph-glands, which experience an 

 especially early development in intra-uterine life. Beside these, 

 only those organs are well developed in the new-born which are to 

 serve the purposes of assimilation, the lungs and the great digest- 

 ive tract, while the poorly developed skeleton and the muscles 

 only form a thin and tender covering to these essential organs. 

 After the great increase in the size of the body during the first year 

 of life comes the period of skeletal development which in the fifth 

 or sixth year is joined by that of the building-up of the muscular 

 and mental powers. Childhood divides itself thus, as this short 

 sketch shows, into a series of phases or periods characterized physi- 

 ologically by the development of definite organ systems. Their sepa- 

 ration is not only justifiable from a scientific, but in a higher degree 

 even from a practical standpoint, for the conditions and necessi- 

 ties of life are so different for each of these periods that the kind 

 of care and treatment is almost exclusively determined by this, 

 that is, by the age of the individual. With the backwardness of 

 development and the slighter variability of life-conditions due to 

 this is connected the fact that the guiding of the life must be the 

 more regular and careful the younger the individual is. Only in 

 later years can individual differences and the influence of social 

 conditions be more marked. 



The most useful division of childhood not only for scientific but 

 also for practical purposes has been found in the threefold divis- 

 ion accepted by Vierordt : 



I. Childhood : Infantia. 



(1) New-born period (first week of life). Characterized by the 



