QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE, 81 



With regard to Gasteropoda, his conclusions are that in 

 all of them the nerves contain myelin, and the same is true 

 of the acephalous mollusks. The tentacular nerves of the 

 Helicina break up near the periphery of the organ into fibrils 

 presenting varicosities, and in their course cellular enlarge- 

 ments are observed, which are analogous to those observed 

 in vertebrate embryos. These fibrils pass in bundles through 

 the true skin and lose themselves in the epidermis, between 

 the large epithelial cells, in the shape of filaments expanded 

 at their extremity. A number of large cells are observed 

 amongst and around the expansion of the tentacular nerve, 

 which are nothing but secreting cells. The arrangement of 

 nerves in the folds of the mouth, &c., is generally the same. 



3. Chrschtschonovitsch (' Reports of the Imperial Academy 

 of Vienna,' Ixiii, 2nd Abth., 301 — 315, " Contributions to 

 the knowledge of the minute nerves of the vaginal mucous 

 membrane") used the gold method ; he describes a subepi- 

 thelial plexus, and non-meduUated varicose fibres running 

 among the epithelial cells. He could find no connection 

 with the nuclei of the smooth muscular fibres, as described 

 by some observers. 



4. Fleischl (' Centralblatt,' No. 42, Oct. 14th, 1871) pro- 

 poses a new method of investigating the surface of the brain 

 under the pia mater. When this membrane is carefully 

 removed, he puts the exposed surface of the convolution 

 into a half-per-cent. solution of nitrate of silver, and 

 after a few minutes into distilled water, by which the surface 

 acquires a brownish-red colour. Then, by passing the edge 

 of a cutting needle very gently over the surface, small 

 fragments of a delicate film which covers the brain substance 

 may be removed. These fragments, when examined in 

 glycerine, show flat polygonal areas, closely apposed, and 

 varying in size from that of a nucleolus to that of a 

 leucocyte. Fleischl considers these areas to represent cells, 

 but reserves a more detailed anatomical explanation for the 

 present, calling the structure simply cuticulum cerebri et 

 cerebelli. 



5. Ranvier has communicated to the Societe de Biologic 

 in Paris the first results of some laborious researches on the 

 minute structure of peripheric nerves, which are thought 

 to throw a new light on their physiological action. 



It is known that chemical changes take place during nerve 

 function ; the nerve substance becomes acid and heat is libe- 

 rated. There must, then, be some osmotic exchange of liquid 

 or gaseous matters, and the histological details appear to 

 show how the exchange takes place. 



VOL. XII. NEW SER. F 



