690 THE CEREBRUM 



volutions of the left side. A person so afflicted is in the same position 

 as one who is spoken to in a foreign language, i.e., he hears the words, 

 but is unable to depict their meaning, because he cannot properly 

 associate them. Wernicke^ recognized at an early date that this con- 

 dition, together with word-blindness, must lead to a loss of speech, 

 because individuals who thus fail in their associations, cannot react 

 to auditory and visual impressions by the production of coordinated 

 sounds. It may also be inferred that they cannot react to these im- 

 pressions by the act of writing for the same reason. The latter condi- 

 tion is known as agraphia, and the former as aphasia. 



THE CENTERS FOR SMELL AND TASTE 



The Location of the Olfactory Center. — The sense of smell is very 

 unequally developed. We have seen that it forms the dominant sense 

 in many of the lower vertebrates; for example, in the fish in which 

 almost the entire., cerebrum is concerned with this function. These 

 animals, however, are not in possession of a true cerebral cortex, the 

 first indications of it appearing in the amphibia and reptilia. Other 

 animals are entirely lacking in olfactory organs ; for example, the dol- 

 phin, porpoise and whale. ^ This divergency enables us to divide 

 animals into two groups, namely into osmatic and anosmatic, and the 

 former again into macrosmatic and microsmatic. As examples of the 

 first kind, might be mentioned the dog, rabbit, rat and opossum and as 

 an example of the second kind, man. 



The acuity of this sense is in keeping not only with the complexity 

 of the olfactory cells in the nasal cavity, but also with that of the 

 association area in the cortex. In the fish, the reactions following 

 olfactory impressions, are still chiefly reflex. A true cortical or psychic 

 element is first imparted to them in the amphibians and reptiles. 

 This statement implies, that beginning with these animals, the ol- 

 factory reflex realm is gradually amplified by a cortical center. As 

 far as man is concerned, this psycho-olfactory region has been lo- 

 calized by Ferrier in the gyrus hippocampi, and particularly in its 

 distal limb, the uncus. This conclusion has been reached partly in 

 accordance with the anatomical data pertaining to the distribution 

 of the olfactory fibers, and partly because the stimulation of this area 

 in monkeys produces movements involving the muscles of the Hps 

 and nostrils of the same side. This effect is similar in character to 

 that produced by inhaling an irritating vapor. It should be remem- 

 bered, however, that reactions of the latter kind are due chiefly to 

 the excitation of the receptors of the trigeminus nerve. Luciani 

 came to the same conclusions as Ferrier, but extended this area some- 

 what to include the subiculum cornu Ammonis. Bechterew,^ on the 



^ Der aphasische Symptomenkomplex, Breslau, 1874. 



2 Zwardemaker, Ergebn. der Physiol., i, 1902, and Herrick, Evolution of 

 Intelligence and its Organs, Science, xxxi, 1910, 7. 



3 Archiv fur Physiol., 1899, SuppL, 391. 



