104 'Journal of Comparative Neurology and Psychology. 



drawing; they correspond to Hatai's Type III. These inter- 

 mediate cells represent the stages through which the small cells 

 pass while developing into the larger ones, a process which, as 

 we shall see, is constantly going on in the growing animal. 



Rawitz ('8o), in studying the spinal ganglia of various animals, 

 had his attention drawn to these small deeply staining cells and 

 came to the conclusion that they were young developing ganglion 

 cells, the immediate result of a supposed — but confessedly un- 

 demonstrated — cell division. As proof he advances his observations 

 that they are seldom found in the grown animal, but, on the con- 

 trary, are relatively frequent in the young, von Lenhossek 

 ('86) does not agree with these statements of Rawitz, for, while 

 he admits that these cells are found more abundantly in young 

 than in adult animals, he has also found them in large numbers 

 in the full grown frogs. "I believe," says v. Lenhossek, "that 

 one may account for the presence of these little cells through the 

 following consistent explanation: while, in the course of embryo- 

 logical development, the majority of ganglion cells become very 

 much enlarged, a part of them as well as their associated nerve 

 fibers stop at lower stages of development; such undeveloped 

 nerve cells represent the little cells under discussion. According 

 to this conception the cells in question would not be young and 

 capable of further development, but represent ganglion cells 

 remaining permanently at primitive stages of evolution." In 

 1895 V. Lenhossek returned to the subject of the significance of 

 the small cells. "It is not superfluous to insist that the smaller 

 cells, even indeed the smallest cells, are not to be regarded as func- 

 tionless rudimentary structures, but as elements which just as 

 truly as the large cells are functional parts of the nervous mech- 

 anism: we find them associated just like the large cells with a 

 process which divides in the typical way" into a central and a 

 peripheral fiber. "Still less is it justifiable to look upon them as 

 young elements still undergoing development. We are dealing 

 here therefore not with cells which will further divide or other- 

 wise develop but with cells which are formed small once 



for all." 



Evidence, to be presented in a succeeding paragraph, sup- 

 ports V. Lenhossek in his contention that the small cells are not 

 young in the sense of Rawitz; but that all, large and small alike, 

 being derived from a cell division at an early embryonic period, 



