1932] Poliak: Afferent Fiber 8ijstems, Primate Cerebral Cortex 19 



used in all the present experiments was that of Marchi which, in my 

 experience, is far superior to any other method, particularly in experi- 

 mental work on the fiber systems. If properly applied, this method 

 ^ives clear pictures of black degenerated fibers contrasting' with the 

 green or yellowish color of fibers remaining normal, a contrast repro- 

 duced in the accompanying illustrations. To obtain sure orientation 

 concerning the extent of the supplied cortical areas or regions, I 

 sketched in various positions each of the operated brains as soon as 

 removed from the skull. The brains were hardened in Miiller's fluid 

 without the addition of formol and further divided in the usual way 

 into thin slabs (1-2 mm.). Each slab was sho^^^l in the orientation 

 drawing and designated with a number corresponding to its position 

 in the brain. After staining in abundant Marchi 's solution and thor- 

 oughly washing in running water, the slabs were once more put 

 together in their natural order, three to five slabs at a time, hardened 

 and dehydrated in pure acetone (to which burned copper sulphate was 

 added) for two to three hours in the thermostat, thoroughly washed 

 in absolute alcohol (to remove the acetone), put into thick celloidin 

 (10-15 per cent), mounted upon wooden blocks (with cork under- 

 neath), submerged for half an hour in pure chloroform tiU the cel- 

 loidin became hard enough, transferred to 80 per cent alcohol, and cut 

 into continuous series. The sequence of numbers of the sections 

 corresponded with the slab sequences in the drawings. (On Marchi 's 

 method consult Lange, Gehuchten et Molhan, Spielmeyer, Schmorl, 

 R. Krause, and Vogt, 1928, p. 472.) 



Since the series of all operated brains were continuous, an accurate 

 delimitation of the cortical areas or regions supplied by the degener- 

 ated afferent paths, or by portions thereof was achieved; in other 

 experiments the areas supplied by association and callosal fibers were 

 delimited. In studying the series, attention was paid to minute details 

 as well as to the main features of various fiber systems. 



In addition to the study of various fiber paths by means of Marchi 's 

 method, a number of experiments were performed on the Macacus 

 Rhesus and on the Java monkey according to Nissl's method: the 

 ' ' Primary Irritation of Cells or the Retrograde Degeneration ' ' of the 

 nerve cells whose axis cylinders were interrupted. (For the descrip- 

 tion of the method see Nissl's article in R. Krause 's Encyclopaedia, 

 p. 1642.) These experiments deal with various problems concerning 

 the finer or "internal organization" of the visual system. It was 

 hoped that by making small injuries of various sizes and localities in 



