364 SERGIUS MORGULIS 



presents an unusual advantage for the study of the transforma- 

 tion of a centripetal stimulus into a centrifugal impulse. 



It has long since been recognized that the central nervous 

 system is a double apparatus consisting of a receptive and an 

 executive portion. Purposely or inadvertently the older physio- 

 logy overlooked, or at any rate failed to realize, the significance 

 of the interlocking mechanism of both of these apparatus. Yet 

 this intermediary point is of the utmost importance, as it is here 

 that the chief nervous processes take place and all factors acting 

 upon the central nervous system are minutely analyzed. The 

 reflex arch must, therefore, be considered as consisting of three 

 parts: the part which commences at any terminal end of a 

 centripetal nerve and leads to a sensitive cell in the brain, an 

 interlinking piece between this and the third part, which is the 

 executive or effective portion of the reflex arch. 



In the study of the physiology of the central nervous system, 

 the first two are of especial significance. From Pawlow's point 

 of view all psychic activity is nothing else than a complex nervous 

 function which is fulfilled by two mechanisms, identified with 

 the first and second portions of the reflex arch. One serves to 

 break up the complexity of the outside factors into their ultimate 

 elements; the other serves to bring various agents of the outside 

 world into temporary association with fundamental organic 

 functions. One is the mechanism of analysers consisting of a 

 receptive organ, its nerve connection and central sensory cell 

 in the brain or cord. 2 The other is the mechanism of conditioned 

 reflexes. The latter has no specialized centre in the cortex such 

 as, for instance, the association centre, but the large hemis- 

 pheres as a whole must be regarded as the special organ of con- 

 ditioned reflexes. Conditioned reflexes can be formed provided 

 the cortical portion of the particular analyser is intact. By 

 destroying different sections of the cortex one or another con- 



2 1 take this opportunity to correct a serious error committed in an earlier com- 

 munication to this Journal. In reviewing the research on auditory conditioned 

 reflexes I have identified Pawlow's analysers with the mechanism of receptors. As 

 will be seen from the above definition the conception of the analyser is more compre- 

 hensive and really embraces the idea of a receptor as one of its elements. The 

 receptor is merely a new term for the old sensory organ, whereas the analyser is the 

 receptor plus its special nerve connection and the corresponding sensory cell in the 

 cortex. It is interesting to state that Pawlow distinguishes besides the ordinary 

 visual, auditory, olfactory, etc., analysers, also a locomotor analyser which signalizes 

 into the central nervous system every movement of the muscles and bones. In the 

 text it is related how such purely locomotor sensations can be made the basis of 

 conditioned reflexes, just as stimulation by light, sound, etc. 



