8 University of California Publications in Anatomy i^^"^- 2 



justifiable since in none of the experiments performed with conscious 

 subjects were any sensations felt when the precentral cortex was 

 stimulated (Gushing, Valkenburg, Berger, Foerster, Mankowski; the 

 only exception I have found is an observation of Ransom's and of 

 Gushing 's, wherein the sensation of motion was recorded although no 

 actual movements were observed). Yet it is difficult to believe that 

 all those results which contra-indicated the restriction of the sensory 

 function to the postcentral region were due to faulty technique or to 

 erroneous interpretation, especially when one compares the large 

 dimensions of the thalamus and the small size of its alleged cortical 

 "representation" (Brodmann's field 1, 2, and 3; compare also Mona- 

 kow, 1914, p. 252). At any rate the problem of the exact relation of 

 the cortical ''sensorium" to the ''motorium" apparently deser\'es a 

 thorough re-study, for it must be admitted that the anatomical investi- 

 gations of Probst, Roussy, et at., were not carried out with sufficient 

 care, or that in experiments and in pathological eases where the 

 thalamo-cortical radiation degenerated, the visual, the auditory, and 

 possibly other systems were erroneously included within it (Probst, 

 Roussy), or the somatic sensory fiber system was only partly inter- 

 rupted (E. Sachs), or possibly part of the degenerated fibers had dis- 

 appeared (Wenderowic). On the other hand, in scarcely any of the 

 physiological experiments involving cortical destruction was the injury 

 strictly confined to the precentral cortex ; hence an accidental injury 

 or perhaps only an indirect impairment of the somato-sensory aiferent 

 path (because of its position near the precentral cortex) might have 

 occurred ; for, of course, this path might conceivably enter the post- 

 central cortex exclusively. A definite decision concerning this is 

 impossible, for our defective knowledge of the exact course and 

 termination of the thalamo-cortical radiation renders adequate ana- 

 tomical control of such physiological experiments scarcely possible. 

 Thus we see that the old question of whether the somatic sensory 

 cortex and the motor cortex are two separate regions or perhaps one 

 common region, a " senso-motorium " of Munl^ and Exner, or possibly 

 a more highly organized, composite sensory-motor organ, cannot be 

 regarded as answered definitely in favor of the dualistic conception, in 

 spite of the popularity of the latter among modern neurologists. Nor 

 can the criteria of students of cortical cytoarchitecture and myelo- 

 architecture be accepted as decisive, as is claimed (Betz, Brodmann, 

 Gampbell, E. Smith, Vogt, Bolton, Mauss, Nanagas, Economo-Koskinas, 

 Goldstein). It is true that the precentral and the postcentral regions 



