59 8 TEXT-BOOK OF PHYSIOLOGY 



criminating points in contact with the skin. A lesion of this area impairs or 

 destroys the power of recognition of objects and establishes the condition of 

 aster eo gno sis. This judgment, however, would also be impaired or abolished 

 if either the tactile or muscle sense were impaired or abolished, since both are 

 necessary factors in the series of events that lead to the formation of the 

 judgment. The existence of such a center has been made highly probable 

 by clinical cases in which astereognosis existed without impairment of either 

 the cutaneous or muscle sensibility. Inasmuch as focal lesions of the parietal 

 cortex give rise to localized impairment of stereognostic perception as well as 

 impairment of the cutaneous and muscle senses, it is stated that the area is 

 also capable of subdivision into smaller areas for the face, arm, trunk and 

 leg (Mills). 



4. The Gustatory Area. The area for gustatory sensibility has been assigned 



to the sub-collateral convolution on the mesial aspect of the temporo- 



sphenoidal lobe. 



Disease processes involving this area give rise frequently to subjective 

 sensations of taste. Electric stimulation of this area in mammals causes 

 movements of the lips, tongue, etc., which are usually associated with sen- 

 sations of taste. 



The afferent pathway by which nerve impulses, developed by action of 

 organic matter in solution on the terminal portions of the gustatory nerves, 

 are transmitted to the cortical area is considered in connection with the 

 sense of taste. 



5. The Olfactory Area. The area for olfactory sensibility has been assigned 



to the anterior portion of the hippo-campal convolution (the uncinate 

 region) and the anterior portion of the callosal convolution or gyrus 

 fornicatus. 



Disease processes in this region give rise frequently to subjective sensa- 

 tions of odors which as a rule are of an unpleasant character. Destruction 

 of this area is followed by a loss of odor sensations. Electric stimulation 

 of this area in mammals was found by Ferrier to be attended with a peculiar 

 torsion of the nostril and lips on the same side similar to the reaction brought 

 about by the application of an odorous substance more or less disagreeable 

 to the nostril. 



The afferent pathway, by which nerve impulses developed in the ter- 

 minal portion of the olfactory nerve by the contact of odorous particles are 

 transmitted to the cortical areas, is considered in connection with the 

 olfactory nerve. 



6. The Auditory Area. The area of auditory sensibility has been assigned 



to portions of the temporal lobe and may be divided into primary and 

 secondary areas. 



The primary area is located in the posterior portion of the super- 

 temporal convolution, and perhaps the posterior portion of the insula. 

 The secondary areas are located one below and in advance, and the other 

 below and some what behind the primary area, both extending into the 

 medi-temporal convolution. 



Unilateral destruction of the primary area is followed, however, only 

 by a partial loss of hearing in the opposite ear, owing to partial decussation 

 of the auditory nerve, which, however, may be recovered from, after a time, 

 owing probably to a compensatory activity of the insular convolution, 



