196 



NATURE 



[July 17, 1919 



as a submarine happens to come within the beam, 

 the sound-waves are reflected and echo effects are 

 obtainable. Success has been obtained in the picking 

 up and closing on a submarine situated more than a 

 mile away. A very important application of an electro- 

 magnetic effect is the Leader gear. A cable is laid 

 on the bottom of the sea along the course of a narrow, 

 tortuous channel leading into a harbour or through a 

 minefield. Alternating currents passed through the 

 cable can be detected on the ship by aural or visual 

 indications, and by these indications the ship can be 

 guided in safety in fog or darkness at speeds as high 

 as twenty knots almost with as much precision as a 

 tramcar over a railway. In water of suitable depth 

 experience shows that it is a simple matter to apply 

 this method for distances as great as fifty miles or 

 longer. 



Invisible signalling by polarised light, or ultra-violet 

 and infra-red radiations has been employed where it 

 is not advisable to use wireless communication. In 

 wireless methods, by the use of oscillating thermionic 

 valves especially, great progress has been made. 

 Some extraordinary advances have been made in the 

 measurement of the pressure of explosive waves. 

 Changes which take place in 1/100,000 of a second 

 have been recorded by the method suggested by Sir 

 J. J. Thomson and applied by Mr. D. A. Keys, in 

 which the inertia of a beam of cathode-ray particles 

 is made use of; such rays are deflected by electro- 

 static and magnetic fields. The advances made in the 

 production of helium warrant the opinion that, had 

 the war continued after November 11, 1918, supplies 

 of helium at the rate of 2,000,000 cubic ft. per month 

 would have been produced within the Empire and the 

 United States, and helium-filled aircraft would have 

 been in service. 



It is im,possible within the limits of our space to 

 deal adequately with Prof. McLennan 's paper, both as 

 regards what science has done in marine problems 

 during the war and the large number of suggestions 

 he makes regarding the application of what has been 

 discovered to peace conditions. 



THE SIGNIFICANCE OF THE CEREBRAL 

 CORTEX. 



T N the series of Croonian lectures delivered at the 

 ■■■ Royal College of Physicians (June 12, 17, 19, 

 and 24) Prof. Elliot Smith claimed that much of the 

 obscurity concerning the meaning of the structure 

 and functions of the cerebral cortex was due to the 

 failure on the part of biologists and physicians to face 

 the fact that the cortex is the organ of intelligence, 

 and its chief significance of a psychical nature. It is 

 no more possible to understand the cerebral cortex 

 without recognising to the full its real purpose than 

 it would be to explain the mechanism of an aeroplane 

 if the investigator ignored the fact that the machine 

 was made to fly. 



The aim of these lectures was to discuss the means 

 whereby the cerebral cortex acquired its supreme 

 powers as the organ of intelligence. Dr. Henry 

 Head's researches have given us a new vision of the 

 meaning of nervous and mental processes, and have 

 provided all workers in neurology with a new 

 generalisation which compels them to review their 

 own work in the light of the new illumination. 



Much that was dark and unintelligible in the evolu- 

 tion of the cerebral cortex acquires a definite signi- 

 ficance W'hen the facts are examined in conjunction 

 with the results of Dr. Head's clinical work and 

 Prof. Sherrington's experimental researches. 



The mammalian cerebral cortex, i.e. the neopallium, 

 is the repKJsitory of past impressions, and these sensory 

 NO. 2594, VOL. 103] 



dispositions profoundly modify the effect produced by 

 the arrival of fresh impulses. But Dr. Head has 

 shown that, in addition, ''the function of the cortex 

 in sensation is to endow it with spacial relationships, 

 with the power of responding in a graduated manner 

 to stimuli of different intensities, and with those 

 qualities by which we recognise the similarity or 

 difference of objects" that appeal to the senses. On 

 the other hand, the appreciation of the affective side 

 of experience, the pleasantness or unpleasantness, and 

 the crude awareness, are functions not of the cortex, 

 but of the thalamus. 



Since the discriminative functions of the cortex are 

 particularly associated with the neopallium, which is 

 found in a fully developed form only in mammals, the 

 first inquiry must be directe^i towards an understand- 

 ing of the psychical activities of the classes of verte- 

 brates other than mammals ; and from such investiga- 

 tions the nature of the circumstances which called the 

 neopallium into being must be determined. 



The fundamental fact in the evolution of intel- 

 ligence is the significant part played by the sense of 

 smell. In the primitive generalised vertebrate it pro- 

 vided the animal with information of varied kinds, 

 but of direct and obvious psychological meaning, by 

 which behaviour was determined in respect of most 

 of those activities that affect the preservation of the 

 individual and the species, namely, the search for 

 food and the appreciation of its quality, the recogni- 

 tion of friends and enemies, as well as of sexual mates 

 or rivals. 



One factor which added to the dominating influence 

 of smell and emphasised the directness of its appeal 

 was the result of the circumstance that in an animal 

 living in the water the sense of smell was very nearly 

 akin to that of taste. When such an animal scented 

 food it got, so to speak, a foretaste of the satisfying 

 consummation of the experience when the food was 

 seized, tasted, and swallowed with a feeling of intense 

 satisfaction. The whole incident, from the first 

 anticipation of the pleasure in store until the satisfy- 

 ing consummation, was under the dominance of the 

 sense of smell, which became more and more intensely 

 stimulated as the animal approached its quarry, until 

 it culminated in the gratification and the appeal to 

 the sense of taste. The affective tone of the sense of 

 smell linked into a connected series all the incidents 

 of this experience, and the psychical Integration that 

 resulted formed the basis of the appreciation of time 

 and space, of memory, the recall of the earlier Inci- 

 dents of the episode, and of anticipation, the end- 

 result and the joyful consummation. 



In the course of the pursuit of its prey the animal 

 is subjected to the influence of manv other circum- 

 stances that appeal to the senses of vision, touch, 

 pressure, temperature, etc., and affect the organs of 

 equilibration ; and the effects of all these events tend 

 to become involved in the process of psychical Integra- 

 tion. When such information as is collected by these 

 other sense-organs acquire some biological signi- 

 ficance to the animal, the visual, tactile, acoustic, 

 and other sensory tracts make their way Into the 

 cortex in increasing numbers : and they stimulate the 

 growth and differentiation of such special receptive 

 areas as the hypopalllum and neopallium. But this 

 does not happen until the reptilian stage of develop- 

 ment Is reached. 



When, attracted bv Its scent, the primitive verte- 

 brate (such as an Elasmobranch fish) Is impelled to 

 pursue Its prey, it circles about In the search because 

 at first it has no more exact Indication of the position 

 of the object of its pursuit than the relative Intensity 

 of the odour as the pursuer moves about. But when 

 it comes within visual range It acquires a more precipe 



