ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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nerve is negatively refractive ; when those of tho conducting primitive 
fibrils predominate, the nerve is positively refractive — facts which ex- 
plain Ambronn’s observations as to the change of optical characters. 
Nerve- cell and ganglion-cell are histologically and physiologically 
diverse ; both have arisen phylogenetically from neuro- ganglion cells, 
which originally are modified sensory epithelial cells. The nerve- 
cell finds its analogue in the muscle-cell. Both are made up of spindles, 
i. e. of elements which are cells or have arisen from endogenously divided 
embryonic cells. A nerve-fibre is either a fused row of nerve-spindles 
or is one nerve-spindle. Of muscle- and nerve-spindles there are two 
types, the massive bundle-like and the hollow tube-like, but both types 
are often combined. The contractile substance and the conducting sub- 
stance are alike intracellular plasmic products, and consist of primitive 
fibrils and of intrafibrillar substance. Each primitive fibril consists of 
one or of several elementary fibrils. The author illustrates his con- 
clusions with especial reference to the Hirudinea. 
Structural Resemblance between Emulsions and Protoplasm.* — 
Prof. 0. Biitschli has been able to make, as we have previously reported, 
extremely fine foams which, to a certain extent, resemble protoplasm in 
structure and even in behaviour. His observations on Protozoa and his 
experiments with foams lead him to the conclusion that the cytoplasm 
and the nucleoplasm have a foam-like structure, and consist of a honey- 
comb-like arrangement of lamellae with fluid or enchylema in the inter- 
spaces. 
The most successful emulsions were made from olive oil, which must 
be heated for 12 days at 50°-60° C., or for a shorter time at a higher 
temperature. This is mixed with finely powdered non-anhydrous 
carbonate of potassium. Eventually a fine soap emulsion is formed, 
which consists of droplets of soap solution surrounded by films of oil. 
A drop of this is put in pure water and examined. Biitschli’s micro- 
photographs show well the intricacy of structure in the froth, the 
general appearance being that of a complex network. Opinions will 
differ as to the degree of resemblance between the emulsion structure 
and that of the cell, but when microphotographs of the two are seen 
side by side a striking resemblance cannot be denied. 
In water the drops of emulsion increase in volume ; in glycerin they 
decrease ; they are permeable by methyl-green ; and the lamellae of oil 
are stainable. Appearances of fibrillation and reticulation, of nodal 
thickenings and striated borders, and even of the radiations associated 
with karyokinesis f are observable. In glycerin the structure may be 
retained for four to six weeks. In various conditions remarkable 
streaming movements occur. Thus if the drops be resting in a weak 
solution of potassium carbonate, under a cover-glass supported on wax 
feet, and if pure water be drawn in, the drops exhibit active movements 
closely comparable to those of Amrebae and capable of persisting for 
hours or even days. These movements depend on surface tensions. It 
is maintained that analogous, but more complicated, changes of tensions 
have to do with the movements of amoeboid cells. 
* ‘ Untersuchungen iiber mikroskopisclie Schaume und das Protoplasma,’ Leipzig, 
1892, 8vo, 234 pp., 6 pis., 23 figs. 
t Sep. Abd. Verh. Nat. Med. Yer. Heidelberg, v. (1892) 14 pp., 2 figs. 
