176 AJSTATOMY OF THE CBNTHAL NEETODS SYSTEM. 



"We are yet far short of answering the question which presents itself at 

 once after these observations: What functions has the primary end-appa- 

 ratus — i.e., the deep center — of the sensory nerves in the brain? We know 

 simply what occurs in mammals when they are deprived of their connection 

 with cortical center. Xow, it is not at all improbable that, in the measure 

 that the psychical activity of the cortex increases, the activity of the deeper 

 center decreases. Fortunately we possess in the teleosts organisms which 

 possess no cortex at all and only the lower centers. On these new observa- 

 tions should be instituted. It is asked : What is the reptile more capable of 

 accomplishing in the realm of smell — in the interpretation of his olfactory 

 perceptions — than a fish, now that it is demonstrated that to the olfactory 

 apparatus of the reptile a cortical center has been added? Similar investiga- 

 tions are needed for the visual apparatus, since a difference must exist be- 

 tween the vision of a teleost, whose oiDtic tract ends in the midbrain, and 

 that of a bird or mammal, which possesses, from the primary optical center 

 to the cerebral cortex, a tract which meets there an extension association- 

 apparatus. 



The brain-cortex enters into connection with a number of connections 

 which are located far posterior to the cerebrum. These come into promi- 

 nence for the first time in all their complexity in the mammals, and we shall 

 have to study them more closely when the mammalian brain is under con- 

 sideration. But as low in the series as the reptiles one finds a portion of 

 the Corona radiata coming from the frontal pole and ending probably in the 

 Thalamus — Tr. cortico-ilialamicus. This very cortico-thalamic connection 

 becomes later very strong, as already incidentally mentioned in the descrip- 

 tion of the thalamic nuclei. Other very thin fasciculi of the Corona radiata 

 have been observed in birds, but, since their termini are insufficiently Icnown, 

 their enumeration would be of little interest here. Though there are in 

 reptiles and birds no cortical connections to parts which lie posterior to the 

 thalamus, yet such connections occur in mammals more and more in the 

 ascending animal series. The cortex becomes ever larger, ever more im- 

 portant for the activity of the animal organism when the mechanisms which 

 develop under the influence of use and thought are perfected. 



The great importance of the brain-cortex for activity in association is 

 evident, not only from the observations which have been made on animals 

 deprived of cortical areas and on men with diseased cortical areas, but also 

 from its structure, since, as you have already seen, the cortex of the reptiles 

 affords extraordinarily great possibilities for association of afferent impres- 

 sions. Innumerable contacts connect there the cells and the tracts of the 

 most varying provinces. In birds, but still more in mammals, there are still 

 several long bundles which pass from one portion of the cortex to another. 

 These are called Association-himdles. In Fig. 121 there may be seen de- 



