internal and external worlds. Thus, your experiments seem to me to be both 

 necessary and important." (Complete Collected Works, vol. I, p. 396, 1940). 



In reality, the investigations of I. S. Tsitovich (1911), who experimented 

 on newborn puppies and showed that natural conditioned reflexes appear as a 

 result (derivative) of the experiences of life, belong to the very earliest investi- 

 gations of Pavlovian physiology on the ontogenesis of higher nervous activity. 



Higher nervous activity of children was studied in detail by N. I. Krasno- 

 gorskiy (1907-1954), A. G. Ivanov-Smolenskiy (1929-1956), N. M. Shchelo- 

 vanov (1925-1930), N. I. Kasatkin (1935-1955), and other investigators. 



A number of Pavlov's pupils investigated the formation of conditioned- 

 reflex activity in the early ontogenesis of animals. The studies were performed 

 on puppies (F. P. Mayorov, 1929-1933), calves (F. S. Pavlov, 1938, guinea pigs 

 (K. L. Golubeva, 1939-1949), and young birds (L. S. Gorsheleva, 1936). 



All the investigators showed that in early ontogenesis the conditioned- 

 reflex activity gradually assumes the full value and high functional formation 

 and vigor characteristic of the adult individuals of the species, with a definite 

 sequence for the exciting and inhibiting processes. In very young animals, 

 conditioned reflexes are formed more slowly and inhibition develops more slowly 

 than in the adults. The inhibitory functions of the cortex generally lag some- 

 what behind the excitation in development. The concentration of the nerve 

 processes is also still very weak at the beginning of ontogenesis, and there is, 

 to the contrary, a predominance of irradiation. Formation of diff"erentiation in 

 very young animals gives rise to subsequent inhibition and sleep, whereas 

 differentiation in older animals is accompanied by positive induction, as a 

 result of the concentration processes that have been formed. 



The great importance of the work of I. P. Pavlov's school on the early 

 development of higher nervous activity in animals, and particularly in man, 

 was also emphasized by N. I. Krasnogorskiy: "Thus, strictly physiological study 

 of cerebral activity in children has become a new and very important subject 

 for pediatric studies. This has enriched pediatrics with knowledge of the work 

 of the higher areas of the brain in children during various age periods and has 

 provided a substantial basis for the further study and physiological understand- 

 ing of the most complex brain processes." (Papers on the Study of the Higher 

 Nervous Activity of Man and Animals, vol. 1, p. 311, 1954.) 



In the years that followed, I. P. Pavlov gave a great deal of attention to 

 the study of the characteristics of higher nervous activity in late ontogenesis. 

 As early as 1912, A. V. Tonkikh carried on investigations along these lines on 

 conditioned reflexes in old dogs. It was already clear at that time that new 

 conditioned reflexes are formed toward the end of life with very great difficulty 

 and are characterized by their extremely temporary character and lability. 

 Further work along these lines was done by L, A. Andreyev (1924), D. A. 

 Biryukov (1929), M. Ya. Mikhel'son (1934), N. A. Podkopayev (1938), D. I. 

 Soloveychik (1932-1938), A. I. Pavlov (1938), G. V. Fol'bort and A. V. 

 Semernina (1940), N. K. Zol'nikova (1940). M. K. Petrova (1938-1953), M. 

 A. Usiyevich (1938-1953), and others. 



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