450 
SUiniARY OF CURRENT RESEARCHES RELATING TO 
mid-brain is composed of two well-marked nenromeres. Evidence of 
the origin of the third and fourth nerves from the two neuromeres of the 
mid-brain is unsatisfactory. 
B. Histolog-y- 
Structure of Amoeboid Protoplasm.* — Prof. E. A. Schafer has suc- 
ceeded, by the instantaneous application of a jet of steam to the surface 
of the cover-glass, in immediately killing blood-cells. The most strik- 
ing point is the contrast between the protoplasm of the body of the cell 
and that of the pseudopodia. For while the former exhibits, according 
to focus, either a finely punctated or a reticular aspect and stains 
decidedly with hsematoxylin, the pseudopodia exhibit not a trace of 
structure, and remain almost entirely unstained. We may conclude, 
therefore, that protoplasm is composed of two parts, which are morpho- 
logically distinct; one exhibits a reticular arrangement and has an 
affinity for haematoxylin, while the other has no structural arrangement, 
and is chemically different. These bodies may be called spongioplasm 
and hyaloplasm ; the former is the firmer, though not, perhaps, actually 
solid, and is, in all probability, highly extensile and elastic; the latter 
flows, and it is by its movement that the movements of cells are pro- 
duced, and it is the more active of the two. Hyaloplasm is probably 
the essential part of protoplasm, but we not yet know how its flowing is 
brought about. 
If the structure of protoplasm be compared with that of striated 
muscle, there may be seen to be many points of coincidence. In the latter 
the substance of the sarcous element stains while the homogeneous 
substance of the clear intervals remains unstained. The changes 
which occur in contraction are so like those which occur in the proto- 
plasm of an amoeboid cell, that it is hardly possible to believe that 
the resemblance is merely accidental. It becomes clear, moreover, that 
neither the protrusion nor the withdrawal of pseudopodia are signs 
of a resting condition ; both are produced by a flowing of the hyaloplasm. 
As to ciliary motion, Prof. Schafer suggests that, if we suppose a 
cilium to be a hollow curved extension of a cell, occupied by hyalo- 
plasm, and invested by a delicate elastic membrane, it follows that if 
there be a rhythmic flowing of hyaloplasm from the body of the cell 
into and out of the cilium, there must be an alternate flexion and ex- 
tension of the process. If the membrane be thickened more on one side 
than another, or if the line of lessened extensibility passed in a cork- 
screw fashion, the spiral direction of certain cilia may be explained. 
Morphology and Physiology of the Cell.j — Dr. A. B. Macallum 
offers some contributions to our knowledge of the cell. He commences 
with a discussion of the nature of structures observed within epithelial 
cells of the alimentary canal. He classifies them thus : — 1, Parasites ; 
2, Remains of broken-down cells and nuclei swallowed by the healthy 
adjoining cells ; 3, Material swallowed by the epithelial cell from food 
passing over its free surface ; 4, Plasmosomata migrated or extruded 
from the nucleus (in the glandular cells of the pancreas only). He 
* Proc. Koy. Soc. Lond., xlix. (1891) pp. 193-8. 
t Trane. Canadian Inst., i. (1891) pp. 247-78 (2 pis.). 
