SENSE AREAS AND ASSOCIATION AREAS. 191 



The Body-sense Area. In his early experiments Munk in- 

 sisted that lesions of the cortex involving the Rolandic area are 

 accompanied by a state of anesthesia on the other side of the body, 

 hemianesthesia, particularly as regards the tactile and muscular 

 sensations. It is not necessary, perhaps, to go into the details 

 of the long controversy that arose in connection with this point. 

 Both the clinical and the experimental evidence has been contra- 

 dictory in the hands of different observers, but the tendency of 

 recent studies has been to phow, as stated above, that, whereas 

 the motor areas lie anterior to the fissure of Rolando, the sensory 

 areas concerned with the cutaneous and muscular sensations extend 

 posterior to this fissure.* Positive cases are recorded in which lesions 

 involving the anterior central convolutions were accompanied by 

 paralysis on the other side, hemiplegia, without any detectable 

 disturbance of sensibility, and, on the other hand, lesions in the 

 posterior central, and neighboring parietal convolutions, in which 

 there was a hemianesthesia more or less distinctly marked without 

 any paralysis. Such cases tend to support the view that the motor 

 and body sense areas, although contiguous, do not overlap. f On 

 the other hand, the embryological evidence, as furnished by Flechsig, 

 indicates that the sense areas may extend in front of the Rolandic- 

 fissure (p. 212) and overlap the motor areas in part. At present, 

 perhaps, one is justified in saying only that the region immediately 

 posterior to the Rolandic fissure is entirely sensory. Regarding 

 the sensory defects associated with lesions of the parietal lobe 

 posterior to the Rolandic fissure (posterior central convolution, 

 supramarginal, superior, and possibly inferior parietal convolutions), 

 it seems probable that they involve chiefly the muscular sense, 

 pressure and temperature sense, and the judgments or perceptions 

 based upon these sensations, while the sense of pain is but little 

 affected. Monakow gives the order in which sensory defects mani- 

 fest themselves after such lesions, as follows: The localizing space 

 and muscle sense are chiefly affected,- in fact, almost lost on the 

 opposite side; the temperature and pressure sense may be affected, 

 while the pain sense is retained or but slightly affected. The 

 clinicians have observed that the most positive and invariable 

 symptom of lesions in this region is a condition of astereognosis, 

 that is, a diminution in the stereognostic sense or perception. By 

 the stereognostic perception is meant the power to judge concerning 

 the form and consistency of external objects when handled, and it 

 must be regarded as a perception based upon localized sensations of 

 touch and temperature in combination with muscular sensibility. 



* Consult Monakow, "Ergebnisse der Physiologic," 1902, vol. i, part I, 

 p. 621. 



t Mills, American Neurological Association, 1901. 



