METHODS OF EESEARCH. 23 



adopted with good results. For the study of the minute anatomy of 

 the bulbs, and of their component elements, the specimen should be 

 macerated in iodine-serum (with or without admixture of a little 

 chromic acid), then placed for a few days in solutions of bichromate of 

 potash, containing 12 parts per cent., to which an equal volume 

 of pure glycerine may be advantageously added. After such prepara- 

 tion, the specimen should be carefully broken up with very fine 

 needles under the simple microscope. For this purpose I strongly 

 recommend the use of extremely fine-pointed glass spiculae, instead 

 of the ordinary steel needles. The spicula3 can be obtained much 

 more sharply pointed, and at the same time are much smoother and 

 less adhesive than steel needles. In order to see the division and 

 terminal distribution of the nerves, sections may be examined that 

 have been made through dried or frozen preparations placed in diluted 

 acetic acid and glycerine. Sections made through fresh, and especially 

 through frozen, preparations, which have been further treated with 

 chloride of gold containing 0*1 0*5 per cent., or withperosmic acid of 

 0-25 2-0 per cent., may also be recommended. For the fine terminal 

 nervous expansion occurring in the mucous membrane close beneath 

 the gustatory bulbs, Schwalbe recommends maceration for several 

 clays in chromic acid of 0-02 per cent., or in solutions of bichromate 

 of potash containing 0-5 to 1 per cent. 



The gustatory organs of the Frog should in the first instance be 

 examined whilst still quite fresh, with the addition only of a little 

 serum. By this means the peculiar epithelium of the gustatory disk 

 can be recognized in the living state, the richly nucleated internal and 

 the non-nucleated external layers are distinguishable, and the mosaic 

 apparent on surface views from above, formed by the extremities of 

 the large cup-cells and the points of the columnar and fork-cells, 

 may be seen as well as the dark-edged nerve fibres and the other 

 tissues of the papillae. The breaking up of the gustatory disks 

 into their elements is best accomplished by the aid of fine glass spiculas 

 under the simple microscope, in preparations which have macerated 

 for a few days in a mixture of equal parts of solution of bichromate 

 of potash containing 0'4 per cent, and strong glycerine, or which 

 have lain for an hour in perosmic acidof 0'5 to 1'5 per cent. The 

 branching of the nerves in the nerve cushion is sometimes beautifully 

 distinct in fresh papilla, if the gustatory disks have previously been 

 separated in serum. They may then be rendered more distinct 

 by the addition of glycerine ; perosmic acid should also be tried. 



F. E. Schulze recommends, for the investigation of the cells in the 



