ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
177 
cytes and the cilia help. But various considerations suggest that proto- 
plasm “ must have the power of actively sucking into itself both colloid 
fluids and solid particles.” In studying the yolk-sac of a trout embryo, 
Czermak observed what he could only interpret as an active suction of 
blood serum from intercellular lacunae into a splanchnopleure cell. 
From each intercellular lacuna there seemed to be a broad stream 
flowing into the cell and dividing into branches. He attributes the 
process to plasmic contraction and calls it myzocytosis. But one would 
like further corroboration. 
Structure of Dentine.*' — Mr. R. R. Andrews finds that two kinds of 
cells are concerned in the formation of dentine ; one, a fibre-forming 
cell, with a long process running into the canals ; the other a matrix- 
forming cell, the true odontoblast. This is usually square and abrupt 
against the dentine, and the processes, which it appears to have, belong 
to the fibre-cells deeper within the pulp tissue. As the dentine layer 
forms, the fibre of the fibre-cell lengthens, and against this lengthening 
fibre the same hyaline layer is formed as against the forming matrix- 
next the formative pulp. All the branching of the canaliculi is due to 
the merging of the fibre-cells, which form branches from the main fibres. 
The so-called sheath of Neumann is but transitional tissue only partially 
calcified, which lines the canals in the dentinal matrix, and is only a 
tube or sheath when acids have destroyed the adjoining more fully 
calcified substance. 
Optical Reaction of Connective Substances to Phenol.f — Herr V. 
v. Ebner finds that the positive double refraction of typical connective 
tissue, cartilage, decalcified bone and dentine, &c., becomes negative on 
treatment with benzophenol (carbolic acid), while the negative double 
refraction of the lens-capsule becomes positive. A reversion also occurs 
in chitin, spongin, mucus hardened in alcohol, but not in muscle, horn, 
starch, cellulose, or cork. Resorcin, trinitrophenol, metakresol, metaxy- 
lenol, kreosol, heavy clove oil, oil of bitter almonds, &c., act like benzol- 
phenol ; some other substances, such as thymol, a-naphthol, hippuric 
acid, diphenylamin, and inorganic substances, do not act. The degree of 
the negative double refraction varies with the concentration of the solution 
and the temperature. The reaction does not depend on the formation 
of any crystalline substance in the tissue, nor directly on histological 
structure, nor on diffraction or capillary processes, but primarily on the 
chemical behaviour of the tissue to the reagent. 
y. General. 
Assimilation and Activity.! — M. P. Yuillemin discusses the two- 
aspects of metabolism which Claude Bernard defined — assimilation and 
disassimilation. He agrees with Le Dantec that the separability of 
these is artificial ; the processes of receipt and discharge are combined 
in limited time and space. We may regard it as highly probable that 
the two phenomena are simultaneous, that one is the counterpart of the 
other. But until analysis has done more to disclose the successive- 
* Ex. Internat. Dental Journ., Nov. 1895, 5 pp. 
t SB. K. Akad. Wiss. Wien, ciii. (1894) [received Dec. 1895] pp. 1G2-88. 
X Comptes' Rendus, cxxii. (1896) pp. 411-2. 
