ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
765 
Although segmentation made some progress, there were no nuclei to be 
seen, and the abnormal process speedily came to a standstill. 
B. Histology* * * § 
Central Corpuscles.* — Dr. R. Tick protests against 0. Burger’s 
interpretation of the central corpuscles as merely the results of the 
attraction and compression of microsomata. He maintains that it is 
warrantable to regard them, especially since they are known to divide, as 
independent specialized constituents of the cell. 
Histology and Micro-Chemistry of Blood.f — Dr. J. Weiss discusses 
in the first place the chemistry of staining. He is emphatic in 
maintaining that it is not an original substance of the tissue which we 
see stained in the preparation, but rather the result of all the chemical 
processes to which the tissue has been subjected. Describing prepara- 
tions of blood after Ehrlich’s methods, he notices that the elective 
power of the cytoplasm of the mononuclear cells is entirely different 
from that of the polynuclear leucocytes. Four kinds of unpigmented 
blood- cells may be chemically differentiated. The polynuclear leu- 
cocytes with eosinopliilous plasma are distinguished from the poly- 
nuclear leucocytes with eosinophilous granules ; the first are again 
distinguished from polynuclear leucocytes with basopliilous plasma and 
these from the mononuclear leucocytes with basophilous plasma. Inci- 
dentally the author notes that the multiplication of the eosinophilous cells 
is quite independent of that of the other leucocytes. Asa contribution 
to the chemistry of the cell-contents, he gives an account of the 
reactions with cinnamylaldehyde, salicylaldehyde, vanillin, &c. 
Nerve-cells of the Sympathetic System of Mammals.^ — Prof. A. 
Van Gehuch ten’s observations have led him to the following general 
conclusions. The nervous elements of the sympathetic are in all points 
comparable to the elements of the cerebrospinal nervous system. Like 
them, they are provided with two kinds of prolongations ; some are 
short, protoplasmic and probably “ cellulipete,” while others are long 
cylinder-axes and probably “ cellulifuge.” The number of protoplasmic 
prolongations is various ; they most often have one or two bifurcations 
before ending in the neighbouring cells, but in some cases they remain 
undivided. They always end freely, and the arrangement in a 
circumcellular nest is accidental, and has not the importance which 
Ramon y Cajal has endeavoured to attribute to it. No nervous element 
has more than one cylinder-axis continuous with a nerve-fibre. 
Structure of Optic Lobes of Chick. § — Prof. A. Van Gehuchten finds 
that in a chick of eighteen to twenty days it is possible to recognize in 
the optic lobe three more or less distinct layers, which correspond to the 
three layers which he and M. Martin have lately detected in the olfactory 
bulb of Vertebrates. The first is the layer of retinal fibres in which 
there terminate by free ramification and in several planes most of the 
fibres of the optic tract, while there are also the terminal ramifications 
* Anat. Anzeig., vii. (1892) pp. 464-7. 
t MT. Embry ol. Inst. K. K. Univ. Wien, 1892, pp. 23-63 (1 pi.). 
X La Cellule, viii. (1892) pp. 83-95 (1 pi.). 
§ Tom. cit., pp. 1-43 (3 pis.). 
