(1) A chaotic period, characteristic of the newborn infant. 



(2) A reflex-experimental period, usually extending to the appearance of 

 speech, or approximately to the beginning of the second year after the child's 

 birth. 



(3) An imitative-practical period, up to school age. 



(4) An imitative-ideational period, the school period up to the age of 20 

 years. 



(5) A critical-creative period, essentially that of mature adults, with some 

 subdivisions." 



This attempt to subdivide the periods of development of the human psyche 

 had an undoubtedly progressive significance for that time. 



Lesgaft gives a remarkable characterization of the early stages of develop- 

 ment of the child's sensory organs and psyche (up to the age of 2 years) : 



"In the newborn infant, the higher senses are still not well enough de- 

 veloped for us to detect any activity associated with them; through their instru- 

 mentality, only some reflex factors receive a signal. The child gradually begins 

 to perceive tactile and muscle sensations, taste, odor, and visual and auditory 

 sensations. But these sensations are not yet diff'erentiated consciously so long as 

 the interaction of the sensations that excite the various sensory organs has not 

 determined their conditionality. It is only then that ideas are formed from sen- 

 sations. In addition to this, the child begins to distinguish the pleasant from the 

 unpleasant: he is a smiler. This occurs before the end of the third or at the be- 

 ginning of the fourth month. The infant goes from a lying to a sitting position 

 at the beginning of the second half of the first year; he begins to crawl and look 

 at everything that surrounds him: he is an observer. During the ninth or tenth 

 month, the infant begins to stand on his feet; he utters some articulated sounds 

 and grasps everything: he is a grasper. During the first half of the second year, 

 the infant moves easily and continues to accelerate his movements: he is a 

 runner, and in the second half of the same year he easily utters articulated 

 sounds and masters more and more words: he is a babbler and imitates every- 

 thing. It is also at this time that he begins to form his habits. Toward the end 

 of the second year or at the beginning of the third, he isolates himself, by making 

 a comparison, from the surrounding environment and speaks of himself in the 

 first person as I." 



At the beginning of the 90's, the studies of I. V. Troitskiy (1890-1912) and 

 especially those of N. P. Gundobin (1891-1912) raised the development of 

 Russian pediatrics to new heights. 



Troitskiy proceeded from a recognition of the singularity of the infant 

 organism and of its qualitative diff'erence from the adult organism: "The infant 

 is not a minature edition of the adult" (A. Jacoby). He emphasized the fact 

 that "the anatomic-physiological modifications that regularly occur in the 

 course of growth, the sensitivity of the child organism in general and of its 

 individual organs in particular, very diff'erent in the various periods, with re- 

 spect to harmful factors, the ability to counteract these, weak at the start but 

 gradually increasing with age: all of this, taken as a whole, gives the pathology 

 of childhood its independent character" (I. V. Troitskiy, 1907). 



1С 



