280 The American Naturalist. [March, 
mingling with one another, and come in contact with the dendrites and 
‘cells of the body. While this explains that the fascicles are composed 
of fibres of but one kind, nothing is known of the fibres that go to the 
ganglia habenulæ to complete the circuit. Hence the function of the 
fascicles is still an open question. 
The most interesting point, besides the solution of the structure, origin 
and termination of the fascicles of Meynert, that appears in the paper, 
concerns the conductive function of the dendrites. Such a function has 
been denied them by Kölliker, who still maintains his original ground. 
His objections are based on the fact, as he states it, of there being proto- 
plasmic processes in certain parts of the white matter of the human 
brain where they cannot come in contact with nerve endings. Now van 
Gehuchten shows that in the anterior lobes the ascending or sensory 
fibres from the basal peduncle terminate freely among the processes or 
dendrites of the cells of the descending fibres, and that there is no 
third cellular element between them. And, what is more to the point 
and of greater weight, he finds that the extremely lengthened den- 
drites of the cells giving rise to the facial nerve penetrate the descending 
root of the trigeminal from the neurites of which are given off short, fine 
collaterals. It has been that shown among Batrachia and elsewhere 
such means of completing the nervous circuit exists, but Kölliker has 
persisted in denying any value to these facts when man is considered. 
The nervous circuit may, he says, be more easily explained without 
the dendrites. To this van Gehuchten adds that the matter would be 
still more simple were the collaterals left out. But dendrites and col- 
laterals exist and it is our business to explain them. Moreover, fur- 
ther study of the brain of the higher animals and of man may, and 
probably will, show that in those places in which Kölliker sup- 
poses none to exist, collaterals really occur; and that their not being 
seen hitherto is to be explained by the difficulties that beset the path 
of the investigator when he takes up so complex and highly-developed 
a structure as the human and mammalian brain. 
It is with considerable force that van Gehuchten finishes his consid- 
eration of the question. From the moment, he says, that any one admits, 
as one must, the conductive function of the dendrites of the mitral 
cells of the olfactory bulb, of the cells of Perkinje in the cerebellum, 
of the cells of the optic lobes in birds, of the ganglionic cells of the re- 
-tilia, of the pyramidal cells of the cerebral cortex, one may demand 
upon what decisive grounds any one can find support for a denial of 
the same function in the dendrites of the medulla. 
—F. C. Kenyon. 
