52 EECOKD OF CURRENT RESEARCHES RELATING TO 



Ganglion-cells in the Arachnoid Membrane.* — Dr. Lowe calls 

 attention to his previous discovery of large ganglion-cells on the 

 olfactory bulbs of the rabbit, lying on the interior layers of the arach- 

 noid. These cells together make up a small ganglion, whose exact 

 position is on the outside of the olfactory nerve-bundles of the bulb, 

 at about the middle of its lateral surface ; it is found represented in 

 every vertical section of the bulb from front to back. The cells lie 

 beneath the investing arachnoid, and the pia mater sends out a sheath 

 which envelopes separately each cell of the ganglion, so that, though 

 closely connected with, it is yet shut off from the nerve-fibres. The 

 cells are round, and exhibit no processes. 



Their function is apparently sensory, and possibly connected with 

 sensations of headache. 



Similar cells are found also on the convex surface of the cerebrum : 

 the arachnoid may be shown to contain them here by transferring the 

 freshly exposed brain to a vessel containing some perosmic acid ; in 

 this case the cells are found sparingly, and here also without apparent 

 connection with the abundant nerves which pass close to them in the 

 membrane. They are round cells, enclosed in distinct capsules, and 

 lie close beside the nerve-stems. 



This is an important addition to our knowledge of the sympa- 

 thetic system, although as long ago as 1850 Luschka and Eudinger 

 had traced sympathetic and other nerves into the dura mater ; later, 

 Eainey and Bourgery demonstrated nerves in the arachnoid, and 

 assigned them to the sympathetic, but neither in these nor other 

 researches had the presence of peripheral nerve-cells been shown. 



Scales of Osseous Fishes,| — Professor Carlet publishes a short 

 memoir on this subject, and the following is a summary of his chief 

 conclusions. The scales are singly or doubly refractive, according as 

 they are young or old ; as the organic matter constituting the scales 

 is always singly refractive, it is clear that the doubly refractive condi- 

 tion is due to its impregnation by inorganic salts, which become either 

 more abundant or more com2)act as the animal grows older ; investi- 

 gations with the aid of picrocarmine reveal the fact that the peripheral 

 and the deeper parts of a scale are younger than the central and the 

 more superficial parts. In those fishes in which the scales are im- 

 bricated, they are placed in hexagonal prismatic cavities, and the 

 facets of these prisms become so folded as to form two planes, one of 

 which becomes attached to the posterior edge of the scale next in 

 front, while the other passes over the subjacent scale. The so-called 

 spinules which are connected with some of the scales, are shown to 

 be hypodermic in origin, just as are the other parts ; and it is by the 

 fact that the scales are not of epidermic origin that we are able to show 

 that they should not be compared with the hairs of mammals or the 

 feathers of birds, which are epidermic structures. The most important 

 point in their " physiology " seems to be that they are only displaced 

 passively ; but this change in their position is easily effected, owing to 

 the extremely loose character of the tissue in which they are implanted. 



* 'Arch. Mikr. Anat.,' xvi. (1879) p. 613. 

 t 'Ann. Sci. Nat.,' viii. (1879) art. 8. 



