218 THE MICROSCOPIST. 



were immersed for an hour or two in a mixture of one part 

 acetic acid and three parts alcohol, to render the gray 

 matter transparent and the fibrous elements prominent. 



Sections may be stained with carmine and mounted in 

 glycerin or balsam (see Chapter Y). 



(6.) Organs of special sense: 



a. Organs of Touch. The tactile papillae of the skin 

 and Pacinian corpuscles may be studied in thin sections 

 of fresh or dried skin. Treatment with dilute acetic 

 acid, or acetic acid and alcohol, and staining with car- 

 mine, or chloride of gold, is recommended. The papillae 

 are made up of connective tissue, into which nervous fila- 

 ments enter, and end in peculiar tactile corpuscles (Plate 

 XXIII, Fig. 173). The structure of the skin itself, with 

 its various layers and sudoriparous glands, may be seen 

 in such sections. 



b. Organs of Taste. The terminations of the gustatory 

 nerves of the tongue are yet imperfectly known. In the 

 circumvallate papillae, on the side walls, certain structures 

 are found, called gustatory buds or taste-cups (Plate XXIII, 

 Fig. 174). They consist of flattened lanceolate-cells, ar- 

 ranged like the leaves of a flower-bud, and containing 

 within them fusiform gustatory cells, which end in rods, 

 and filaments projecting from the rods above the buds 

 are seen in some animals. Underneath is a plexus of pale 

 and medullated nerve-fibres. The mode of nervous ter- 

 mination in the fungiform papillae is not known. For pri- 

 mary examination, sections of the dried tongue may . be 

 softened in dilute acetic acid and glycerin, or hardened in 

 osmic acid. For the finer structure, maceration in iodine 

 serum, and immersion in one-half per cent, chromic acid, 

 with an equal quantity of glycerin, is recommended. 

 Careful picking under the simple microscope is necessary. 

 Sections may also be stained with chloride of gold. 



c. Organs of Smell. In the olfactory regions, which are 

 patches of yellowish or brownish color on the upper and 



