952 



compare briefly the results arrived at by some of the previous 

 investigators of this subject. The latter have, however, worked with 

 uiyeiins sheath staining methods and have determined the number 

 of meduliated nerve fibres in different states. 



Dunn ') *'A considerable increase in the number of meduliated 

 nerve fibres occurs during the early life of the albino rat". Dunn 

 investigated the ventral root of Oil in M?is novjneg. albinus. The 

 same thing is true, according to Hatai ') of the "albino rat" with 

 regard to the ventral roots of CVI, 7% IV and jL li, and, according 

 to BouGHTON '), with regard to n. occulomotoriiis in the same animal. 

 Boughton's investigations (06) about cognate problems in the cat and 

 WiLLEMs's *) in the rabbit point to the same conclusion. 



Dunn states: "Ranson's records then are comparable with those 

 presented now, and together they show that in regard to the second 

 spinal nerve of the albino rat the number of meduliated necve fibres 

 in both the dorsal and ventral nerve roots increases during the life 

 of the individual, but that the greatest increase occurs before the 

 sexual maturity or so-called puberty of the animal," and so on. It 

 is thus shown that what is true in this res{)ect for all the axons — 

 as shown by the results of the calculations given in the above table — 

 is also true for only the meduliated nerve fibres. The percentage of 

 increase obtained by using myelin sheath staining methods on the 

 material in question is considerably larger than that arrived at by 

 impregnation of the axons. This is due to the fact that the young 

 animal has relatively considerably more axons free from medullary 

 sheaths than the older one. This increase in the number of nerve 

 fibres is decidedly larger in the dorsal than in the ventral roots, a 

 fact which is seen most clearly when the comparison is based on 

 the conditions in a rather large number of animals. This is not so 

 striking in Cmiis, and Mus rattus shows an entirely reversed state 

 of affairs. These apparent exceptions are, however, probably due to 



1) Dunn, Elisabeth Hopkins. The influence of age, sex, weight and relation- 

 ship upon the number of meduliated nerve fibres and on the size of the largest 

 fibres in the ventral root of the second cervical nerve of the albino rat. The 

 Journ. Gomp. Neur. Vol. 22. N'>. 2. 1912. 



') Hatai, Shinkiski. On the increase in the number of meduliated nerve fibres 

 in the ventral roots of the spinal nerves of the growing white rat. J. Comp. Neur. 

 Vol. 13, 1903. 



3| BouGHTON, Thomas Harris. The increase in the number and size of the 

 meduliated fibres in the occulomotor uerve of the white rat and of the cat at 

 different ages. J. Gomp. Neur. Vol. 16. 1906. 



*) WiLLEMS, Edguard. Localisation motrice et kinesthesique. Les noyaui 

 masticaleur et mesencephalique du trijumeau chez le lapin. Le Neuraxe t. 12, 1911. 



