236 Dr. Burneti’s Reviews and Abstracts 
however, as will be seen, is Kélliker. Judging from his state- 
ments and his still more numerous figures, there would appear no 
doubt that nerve-fibres may and do arise from the vesicular 
centres. (See especially the numerous figures in his “ Mikrosco- 
pische Anatomie,” 1, p. 390-546. 
After the most careful study of the intimate structure of the 
nervous centres of frogs, Prof. Wyman has failed to observe any 
thing of this direct anatomical relationship between the two por- 
tions of nervous substance. Liedy’s observations on the micros- 
copical structure of the nervous centres of the terrestrial Gastero- 
_poda, sustain also the view of the non-direct connection. (See 
“ The terrestrial air-breathing Mollusks of the United States, by 
Amos Binney. ited by Dr. A. A. Gould. pecial Anatomy, 
by Letdy, vol. i, p. 243.) To this the writer may add his own 
experience of the same import. He has invariably failed to detect 
the direct continuity of these parts, and in some special researches 
made sometime since on the intimate structure of the human 
brain, nothing of the kind warranting Kélliker’s opinions was — 
This discrepancy of results is not a little remarkable, and al- 
though from the character and the amount of the authority in 
favor of the direct connection of vesicles with nerve tubes, there 
can be no reasonable doubt that such relations do occur; yet it 
may be very justly asked if this connection when present, is not 
the exceptional condition, and one wholly unessential to the 
mutual physiological relations of the nerve-cells and nerve-tubes. 
If it is necesssary for the transmission of nervous power, that the 
nerve-tube should be directly continuous into the nerve-cell or 
vesicle, then it would be supposed that all nerve-fibres must ter- 
minate in this manner. This, as is well known, is not the case. 
The writer has had the good fortune to be able to watch the 
phases of nerve formation from the earliest point to the complete 
condition, and it has occurred to him that these curious phenomena 
in question, might find some explanation in the probability of some 
of the old nuclei of the nerve formation, producing a cell within 
the confines of the nerve tube, and thus giving rise to a vesicular 
expansion. Some appearances have been observed rather favor- 
ing this view, but we adduce it only in a suggestive light. he 
whole subject deserves special attention from our best microsco- 
pical observers in anatomy. oe 
From a consideration of the intimate structure of nervous tis- 
sue, our author passes to Section III, on the spinal cord. Space 
allows us to make but a single extract which we select upon 2 
point of more general interest. : 
“The change of form which the spinal cord undergoes during 
the progress of development is one of the most interesting fea- 
tures, and one which long since attracted attention. ‘The phases 
