586 TEXT-BOOK OF PHYSIOLOGY 



of muscle sense without impairment of the tactile sense, not infrequently 

 they coexist. Surgical removal of a small angioma posterior to the post- 

 central convolution and about the junction of the super- and sub-parietal 

 convolutions was followed by a loss of the muscle sense in the opposite hand 

 and forearm without any disturbance of other sensations (Starr and McCosh). 

 In addition to sensations of passive position and direction of movements, 

 the sensations of temperature and deep pressure are also associated with 

 the physiologic activities of this region of the parietal lobe. There is much 

 obscurity as to the location, however, of the area in which sensations of pain 

 are evoked. These two areas together constitute the area of the body-feelings 

 or the someaesthetic area. 



Subdivisions of the Cutaneous and Muscle Sense Areas. Clinic observa- 

 tions and post-mortem findings also warrant the deduction that the general 

 areas of cutaneous and muscle sense areas are physiologically subdivided 

 as is the general motor area (see page 590) into areas for the skin and 

 muscles of the face, arm, trunk, and leg which occupy respectively areas 

 that adjoin the corresponding subdivisions of the motor area representing 

 these parts of the body (Mills). On the mesial surface of the cerebrum there 

 are sensor areas for a portion of the leg, anus, genitalia and viscera. 



The afferent pathway through which the nerve impulses, developed in 

 the sense-organs of the skin, tendons and muscles, pass to the cortical areas 

 and evoke the characteristic sensations has been described on pages 544 

 and 545. 



3. The Stereo gnostic Area. The area of stereognostic perception. Stereog- 

 . nosis is the recognition of an object when placed in the hands, through 



its form, density, temperature, etc. The area associated with stereog- 

 nostic perception has been assigned to a portion of the super-parietal 

 convolution and to the precuneus. 



This perception depends on the integrity and cooperation of the tactile, 

 the pressure, the temperature and muscle senses as well as the power of dis- 

 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 eognos^s. 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 



