FATTY DEGENERATION. [ 31G ] 



FEATHERS. 



present all the varieties of arrangement in- 

 termediate between it and Tendon. 



FATTY DEGENERATION. See De- 

 generation, Fatty. 



FATTY TISSUE, or Adipose Tissue. 

 — This is formed of colourless cells, with a 

 very delicate, transparent, structureless cell- 

 wall, enclosing, in the normal state, glo- 

 bules of yellowish fat (PI. 49, fig, 41 ). The 

 cells generally occur in groups, surrounded 

 by or imbedded in connective tissue. They 

 are rounded when isolated, or polygonal 

 when aggregated, and from 1-800 to 1-300" 

 in diameter ; and the fat so fills them, 

 that neither the nucleus which they contain 

 nor the cell-wall is visible. The fat may 

 be removed by drying them, and digesting 

 with ether, when the cells appear contract- 

 ed and wrinkled. In emaciated and drop- 

 sical subjects, each cell contains a number 

 of small globules of fat, frequently of a 

 reddish colour (PI. 38. fig. 3), together with 

 serum, and the nucleus is very distinct. 

 Sometimes in these cases the cells are some- 

 what spindle-shaped or stellate. The fat con- 

 tained in the cells is ordinarily in a liquid 

 state ; but sometimes the margarine separates 

 in the crystalline form (PI. 11. fig. 15 a). 



In the mammalia generally the fatty 

 tissue occurs in the same localities, and has 

 the same structure, as in man. In fishes, 

 the fatty matter is deposited principally in 

 the liver. In reptiles, it occurs chiefly in 

 the abdomen : thus in the frog and toad it 

 forms long appendages occupying the sides 

 of the spine. In birds, it exists chiefly be- 

 tween the peritoneum and the abdominal 

 muscles, and in some of the bones. In many 

 of the lower animals it appears to exist in 

 the state of solution only. 



Fatty tissue is formed from connective- 

 tissue cells. 



Fatty matter may be deposited in cells 

 of all kinds, as in fatty degeneration. 

 During the development of cells, it exists in 

 solution. The action of solution of potash 

 is often of service in distinguisliiiig globules 

 of pi\)toplasm, which have a high refrac- 

 tive power, and much resemble those of 

 fat, from this substance, as it dissolves the 

 former, but not the latter ; solution of osmic 

 acid renders fat-globules black. 



J5inL. Todd and JJowman, Flti/s. of Man ; 

 Kiilliker, Mik7: An. ; Klein, Hist. 42 ; Frey, 

 Hist. 



FAUJASINA, D'Orb.— A delicate and 

 handsome Foraminifcr, but not typical. 

 F. carinata, D'Orb., found in the Maes- 



tricht Chalk, is a thin asymmetrical (plano- 

 convex) Poli/stomella, somewhat thinner or 

 flatter than P. maceUa (F. & M.), which is 

 a subcomplanate, perhaps starved, variety 

 of P. crispa (Linn.), 



BiBL. Parker and .lones, Ann. N. H. 3 ser. 

 V. 104 ; Carpenter, Introd. 213, 286. 



FAVEL'LA.— A form of the concepta- 

 cular fruit of the Florideous Algpe, where 

 the spores are collected in spherical masses 

 situated wholly upon the external surface of 

 the frond, as in Ceramium and Callifhamnion, 



FAVELLIDTUM.— A form of the con- 

 ceptacular fruit of the Florideous Algte, 

 where the spores are collected in spherical 

 masses attached to the wall of the frond or 

 imbedded in its substance, as in Hahjmenia 

 and Dumontia. The term is usually ex- 

 tended to similar fruits not perfectly im- 

 mersed, e. g. those of Gigartina, Gelidium, 

 &c., where they form tubercles upon the 

 branches. Sometimes these tubercles open 

 by a pore on the surface, when mature, to 

 emit the spores. 



FA'VUS (Pon-igo in part, Willan and 

 Bateman). — A disease of the skin, character- 

 ized by the presence of cup-shaped isolated 

 or aggregated crusts, consisting of a Fungus. 

 (See AcHORiON.) 



FEATHERS or Birds.— Feathers agree 

 in all essential points of structure with the 

 hairs of other animals. 



Each feather is composed of a quill (con- 

 taining the pith), a shaft, and a vane or 

 beard with its barbs. The whole consists 

 of a number of epidermic cells, often con- 

 taining pigment, but in most parts so con- 

 solidated or fused together as to be imper- 

 ceptible. 



In the quill, the cells are flattened, elon- 

 gated, and arranged with their long axis in 

 the direction of that of the feather, and 

 their nuclei have the same form as those 

 of the corresponding part (cortex) of the 

 human hair. The cells of the pith are often 

 undistinguishable in old feathers, whilst in 

 the younger ones they are veiy distinct, 

 rounded or polygonal, and contain air. Tlie 

 sliaft and the barbs exhibit the some cortical 

 and medullary structure ; the latter is often 

 beautifully distinct (PI. 22. figs. 14 & 15 c), 

 and causes them to resemble closely the 

 hairs of some Rodents. The barbs are some- 

 times furnished with secondary barbs, or 

 barbules, resembling them in form, but dif- 

 fering mostly in the absence of the pith. 



Featliers are diiveloped in a capsule, and 

 from a pulp or matrix, as in the case of 



