18 University of California Puhlications in Anatomy [Vol. 2 



and pathological studies which are often ambiguoiLS, indispensable as 

 they may be. And lastly, mention must be made of the scant applica- 

 bility of Weigert's and similar methods of staining-, applied almost 

 exclusively in previous investigations of human pathological material, 

 a fact which, though not admitted by many investigators, accounts 

 for the limited results of most of these studies. 



The present plan involves at first a systematic investigation of the 

 three main afferent pathways of the cerebral cortex: the somatic 

 sensory, the auditory, and the visual. The next step, especially after 

 the projection areas of the cortex of the above mentioned afferent 

 paths are determined, will be to study the manner of spread or diffu- 

 sion of the respective impulses from each of the projection areas or 

 "gateways" of the hemisphere to other areas and regions of the cor- 

 tex. The third objective will be the study of the interrelationships of 

 various areas and regions of the same and of the opposite hemisphere 

 as well as of their efferent connections. It will be granted that this 

 extensive plan is costly in time and effort, yet sufficient progress has 

 now been made to warrant publication of the conclusions reached with 

 regard to the afferent paths. The conclusions rest on repeated re- 

 examination and analysis of the preparations. A detailed description 

 of experiments on afferent paths, with due consideration of previous 

 investigations and with conclusions important for physiology, 

 pathology, and psychology will, therefore, be given in the present 

 monograph. In a few places the results of other original experiments 

 on the association, callosal, and efferent fiber systems will be men- 

 tioned but only when they stand in close relation to the investigated 

 afferent paths. 



To obtain results applicable to human physiology and pathology, 

 the present experiments were carried out on monkeys (Macacus rhesus, 

 except in Experiment V-a, V-b, V-d, and V-e where a Java monkey 

 was used). As far as the afferent paths are concerned, my attempt was 

 to interrupt the fiber systems in question either at their diencephalic 

 origin or close to it. Thus I hoped to bring the investigated afferent 

 paths to a partial or a complete degeneration, avoiding at the same 

 time as far as possible other fiber systems. It was my intention to 

 trace the secondarily degenerated afferent fibers to their respective 

 terminations in the cortex and to study: (a) the extension or the 

 boundaries of the "primary" or projection areas of the cortex, (h) 

 the finer relation of the afferent fibers to the cortex, and (c) the inter- 

 nal arrangement of the three investigated afferent paths. The method 



