436 Prof. G. Retzius. Principles of the [June 15, 
their continuous connection one with another by means of fibrilliferous 
anastomoses, either from cell body to cell body or from process to process, has 
once more come to the front during the last few years and divided investi- 
gators into two different camps. As above mentioned, it was shown by His 
that the nerve-cells of the central organ do not anastomose with each other 
during the first stage of their development, but are independent cell entities. 
This has been confirmed by most of the specialists (Cajal, v. Kolliker, 
v. Lenhossék, myself, Van Gehuchten, etc.), who have made an intimate study 
of the development of these organs in the embryo.* 
There has long existed a theory diametrically opposed to that of His, 
respecting the origin of the peripheral nerve-fibres; it was first brought 
forward by the great embryologist Balfour, and has been since vigorously 
‘upheld by a number of other investigators. Their theory is that the nerve- 
fibres owe their formation to special cell chains which are to be found 
in the various parts of the body from the beginning, or, at any rate, very early. 
Among the supporters of this cell-chain theory, however, one, the renowned 
embryologist Dohrn, has lately announced, that on the strength of his most 
recent investigations, he has been obliged to give up his earlier opinion 
entirely, though he had been convinced before of its correctness.. Dohrn must 
therefore not be counted any longer as an exponent of the chain theory. 
Oscar Schultze 1s at present the foremost upholder of this theory. The 
results of several investigators, however, are at direct variance with his. The 
last researches of v. Kolliker, completed just before and published shortly 
after the death of the great anatomist, prove with convincing clearness that 
the nerve-fibres grow out of the central organ towards the periphery. Cajal’s 
numerous researches tell the same story. 
But still more conclusive, if possible, is the work of R. G, Harrison, the 
* Among the adherents of the neurone theory, the Russian neurohistologist Dogiel, 
who, especially with the methylene blue method, has made brilliant discoveries in the 
field of the peripheral nervous system, has pronounced (1904) a theory which is some- 
what different from that of the other neuronists. Dogiel thinks that in the central organs 
certain colonies of nerve-cells form units by means of their dendrite processes: here 
“verbinden sich somit die Nervenzellen einer Art vermittelst ihrer Dendriten zu Zell- 
kolonien ; die in den Bestand aller Zellen einer Kolonie eingehenden Neurofibrillen 
bilden Reihen von geschlossenen und eng miteinander verbundenen Netzen, welche mit 
dem Neurofibrillensystem anderer Kolonien, mit welcher die erstere funktionell 
verbunden ist, organisch nicht zusammenhiangen.” 
In the central organs of the higher animals, I do not know of any proved instances of 
such colonies of nerve-cells, and in the lower animals I have never found them. This year 
Dr. Deineka, working in the laboratory of Professor Dogiel, in his researches on the 
nervous system of Ascaris, has come to the conclusion that the motor and sensory systems 
do not unite with each other per continuitatem, but by contact ; the sensory cells, however 
form organic continuities with each other. 
i i Mt 
