ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
19 
hitherto been regarded as origins in a fibrous network are nothing 
more than the terminal branches of sensitive elements. The origins are 
either from central cells, as in the motor cerebrospinal fibres, the motor 
elements of the sympathetic, all centrifugal fibres of the central organs, 
most sensory peripheral tracts, and all centripetal fibres of the higher 
order, or, like the fila olfactoria, they arise from peripheral cells. 
(2) The nerve-cells possess only partly one kind of process, and only 
partly two kinds of processes, nervous and protoplasmic (dendrites). 
(3) The nervous processes are single — as all cells of the medulla and 
most of the brain, double — as the spinal ganglia of fishes, &c., or nume- 
rous, as the sympathetic ganglia, and some ganglia of Invertebrates. 
(4) With regard to the course they take, nervous processes are 
divisible into those which, after a shorter or longer course, pass into 
centrifugal or centripetal fibres, and into those which break up into a 
number of fine terminal branches. 
(5) It is possible that there are nerve-cells which have no so-called 
nervous processes, but only dendrites. 
(6) In certain nerve-cells (higher sensory organs, part of brain, 
cerebellum) the dendrites appear to have nervous functions, while in 
others they have not. In all cases they have a nutritive significance. 
(7) All processes of nerve-cells, whether protoplasmic or nervous, 
end freely, without forming anastomoses ; consequently all passages 
from fibres to cells, and inversely, and from fibres to fibres, are effected 
by contact. 
(8) Nerve-cells as much as nerve-fibres are active elemeuts of the 
nervous system, and there is every reason for ascribing to them alone the 
higher nervous functions — sensation, motor impulses, and the jisychical 
functions. 
Some of these points require further proof. 
Minute Structure of Human Spermatozoa.* —Prof. K. Bardeleben, 
who stated that he had an opportunity of seeing the preparations of 
Mr. E. M. Nelson in the company of Mr. Beck, gave an account of his own 
more recent studies. The head of the spermatozoon consists, in addition 
to the “head-cap” and “spear,” of an anterior and a posterior portion, 
which exhibit different reactions to colouring matters. The anterior 
part consists essentially of protoplasm ; it is clearer than the hinder part, 
and generally stains feebly or not at all. The hinder parts exhibit a 
distinct cross-striation like muscle. A very delicate protoplasmic fringe 
extends from the anterior part of the head backwards to the “ proto- 
plasmic remains ” on the neck and mid-piece. In the head there is an 
internal body,” which has already been detected by F. Miescher and by 
Ballowitz. It is clear, highly refractive, and either does not stain or 
only stains feebly ; in it may be detected lines of separation, or it may 
be broken up into two, three, or four pieces. In rare cases phenomena 
of division may be observed. 
The central filament of the tail and mid-piece may be followed as 
far as the anterior tip of the head ; the latter is continued forwards into 
an unsymmetrically placed process which, when longest, may be twice 
as long as the head ; it is immeasurably thin, and consists of extra- 
* Yerhandl. Anat. Gesell. (Jena), 1891, pp. 157-C4. 
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