TONGUE. 



[ 645 ] 



TORULA. 



coat (c), continuous with the deeper portion 

 of the mucous membrane, and lined in- 



Fig. 760. 



Two human filiform papillae, one with epithelium. 

 p, p, papillae ; a, v, artery and vein, with the capillary loops ; 

 e, epithelial covering ; /, its processes. 



Magnified 35 diameters, 



ternally by a prolongation of the mucous 

 membrane with papillae and epithelium (a, 

 b) ; and between the two are closed capsules 

 or follicles (g), imbedded in a fibrous and 

 vascular basis. The follicles are from 1-120 

 to 1-48" in diameter, rounded or somewhat 

 elongate, whitish, composed of a coat of 

 areolar tissue without elastic fibres, and with 

 greyish white contents consisting of cells 

 1-6000 to 1-4000" in diameter and free 

 nuclei. 



The tongues of the Mollusca have long 

 formed interesting microscopic objects, on 

 account of the elegant horny (or chitinous ?) 

 teeth placed upon them in numerous rows, 

 and in various patterns; the number and 

 arrangement of which are also of importance 

 in characterizing the families, genera, &c. 



They may be easily examined in the limpet 

 (Patella), the whelk (Buccinum), or in the 

 freshwater snails, Lymnceus, Planorbis, &c. 



BIBL. Kolliker, Mikrosk. Anat. ii.; Todd 

 and Bowman, Physiol. Anat. &c. ; Mollusca : 

 Woodward, On Shells ; Gray, Mic. Journal, 

 1853. p. 170; Siebold, Vergleich. Anat. 



TONSILS. These organs may be re- 

 garded as consisting of from ten to twenty 

 follicular glands, resembling those found at 

 the root of the tongue, surrounded by a 

 common fibrous coat or capsule. 



The blood-vessels are numerous, forming 

 elegant networks around the follicles. 



BIBL. Kolliker, Mikroskop. Anat. ii. 



TOPAZ. The crystals of this mineral 

 belong to the rhombic or right rhombic 

 prismatic system. They consist principally 

 of silicate of alumina, with the fluorides of 

 aluminium and silicium. 



Sections of topaz exhibit remarkable 

 microscopic cavities, often of most singular 

 and elegant forms, frequently containing 

 crystals and one or two non-miscible liquids ; 

 the latter sometimes including bubbles of 

 gas, vapour or vacuities. 



Sir David Brewster recommends the sphe- 

 rical cavities as the best objects for exami- 

 ning the aberrations of lenses, and as infi- 

 nitely preferable to the globules of mercury. 



BIBL. Brewster, Edinb. Phil. Trans, x. & 

 xvi., Treat, on the Microscope, 186. 



TORTOISE-SHELL. SeeSHELL(p.575). 



TORTULA, Hedw. A genus of Mosses. 

 See BARBULA. 



TORULA, Pcrs. A genus of Torulacei 

 (Coniomycetous Fungi). The plants ordi- 

 narily referred here appear to be somewhat 

 heterogeneous in their nature. In what may 

 be considered as the true species, the chains 

 of spores form the principal bulk of the 

 plants, little or no filamentous mycelium 

 existing. Other forms very generally in- 

 cluded under this head agree in their cha- 

 racters with OIDIUM, which itself is a 

 doubtful genus, probably founded on the coni- 

 diferous states of more perfect kinds. But in 

 T. sacchari (or Cerevisice), the Yeast fungus, 

 usually referred here, we find both forms 

 presented; for when actively vegetating in 

 fermenting liquids, it presents the characters 

 shown in fig. 23. PL 20, while, when the 

 liquid becomes exhausted, portions of the 

 fungus float to the top, and produce a fila- 

 mentous structure, terminating in chains of 

 " spores," such as are represented in fig. 24 

 (PL 20), and in fig. 761. The simply beaded 

 form is taken as the type of a genus Cryp- 



