Literary Notices. cxxxix 



\Ye cannot forbear adding tliat the obvious influence of a strongly 

 supported histogenetic hypothesis has been 'a serious detriment to the 

 theoretical portion of the work. Even our elementary text books teach 

 that the peripheral nerves are formed as the outgrowths of a single cen- 

 tral cell. Such outgrowths being, accordingly, in some cases, several 

 feet long (Martin's Human Body.) So far as can be gathered, this is 

 pure assumption and is inherently very improbable. Study of the growth 

 of nerves in embryos of serpents, amphibians and mammals, has con- 

 vinced the writer that, in some cases at least, the growth is by monili- 

 form adhesions of neurons. The process is essentially the same as that 

 occurring in the tracts of the cord where the longer reaches of tracts are 

 in like-manner thus formed. When definite functional paths are formed 

 the nuclei are relieved of part of their function and a variety of subsidi- 

 ary processes resembling fatty degeneration occur, and in this way sheaths 

 are formed. The case ofthe olfactory is therefore simply a striking illus- 

 tration of the normal process which is less clearly seen elsewhere. If 

 this be accepted, it may be admitted that the effect of a proliferating 

 nerve upon the developing adjacent tissues may for a time be less de- 

 pendent on the central than the peripheral neurons. 



It is not a little strange that a second work covering the same 

 ground, with similar methods should appear at nearly the same time.l 



TTiis paper was awarded the medical prize of the Faculty of Wiirz- 

 burg University for 1S91. 



The author's summary is substantially as follows : After an injury 

 to a peripheral nerve destroying its substance at any point, the entire 

 peripheral portion, as well as a short part of the central stump, degener- 

 ates. Healing by first intention does not occur. The degeneration of the 

 immediate vicinity of the wound is followed, 48 hours after, by a par- 

 alytic degeneration of the peripheral part, which is due to various causes. 

 The axis cylinder gives up fluid and grows smaller, Its shrinking pro- 

 duces fragmentation of the sheath. The contraction of these fragments 

 produces a corresponding rupture of the axis. At about the fourth day 

 the nuclei of Schwann's sheath begin to proliferate and the proto- 

 plasm increases, which process perhaps assists in the degeneration. The 



1. NoTTHAFFT, A. F. N. NcuG Untersucliungeu ueber den Verlauf cler Degener- 

 ations- unci Regenerationsprocesse am verletzten peripheren Nerven. Zeltsch. f. wis. 

 Zool., LV, 1. Nov., 1802. 



