Dunn, Nerve Fibers of the Frog. 325 



white substance of the spinal cord certain fibers occur which 

 decrease in diameter at lower levels. His conclusions, how- 

 ever, are vitiated, as are those of other of the earlier histolog- 

 ical investigators, by the crudity of the techinque of that 

 period. 



ScHWALBE, (1882, p. 40) in the paper already quoted 

 touches upon the question of conical diminution in the peri- 

 pheral nervous system. After referring to the findings of 

 Henle, Kolliker and others, in which the smaller size of the 

 motor and sensory nerve fibers near their terminations was 

 recognized, Schwalbe states the conclusions at which he had 

 arrived from his own observations. These observations con- 

 sisted of the measurement of fibers in the trunks of nerves 

 destined for the muscles or the skin and again upon the corres- 

 ponding fibers near their destinations. 



His conclusion is in this sentence, p. 44: "Beide zeigen 

 Verfeinerungen nach der Peripherie, die motorischen aber erst 

 an der zahlreichen Theilfasern unter Querschnittszunahme der 

 gesammten motorischen Nervenbahn ; die sensiblen Fasern 

 verschmalern sich dagegen schon vor der Theilung unter be- 

 deutender Querschnittsabnahme der sensiblen Bahn ! " 



Of the later authorities Kolliker, 1896, in his condensa- 

 tion of the subject of nerve fiber diameter states that some 

 fibers are smaller near the nerve cell than at a greater distance 

 and that certain fibers, notably the sensory fibers, diminish in 

 diameter near the periphery. He reaches the conclusion that 

 the entire subject of nerve fiber diameter has not been suffi- 

 ciently worked over to make possible any definite statements 

 regarding it. 



Since, then, the observation of Schwalbe regarding the 

 lessening diameter of nerve fibers at the periphery is the only 

 one based upon observations made upon fibers from mixed 

 nerves between the joining of the spinal roots and the periphery, 

 the present observations are offered in partial confirmation of 

 the theory of conical diminution of peripheral nerve fibers in 

 their course. 



-The special interest of these findings centers in the fact 



