gyrostatic 
A system of four gyrostatic masses connected together 
by links was shown to possess all the properties of an or- 
dinary elastic spring, although composed of matter in it- 
self entirely devoid of elasticity. 
Sir W. Thomson, quoted in Science, IV. 249. 
gyrqvagi (jl-rov'a-ji), n. pi [ML., < L. gyrus, 
a circle, + vagus, wandering.] In the early 
I'hurch, vagrant monks without definite occu- 
pation, who subsisted upon the charity of 
others. 
Gyrovagi, vagrant tramps who even at that time [528], 
as more than a century earlier, continued to bring dis- 
credit on the monastic profession. Encyc. Brit., XVI. 704. 
gyrus (ji'rus),w. ; pi. gyri (-ri). [L., NL., < Gr. 
}iYof, a circle, circuit, ring; cf. yvp6^, round: 
see gyre,] In anat., one of the rounded ridges 
into which the surface of the cerebral hemi- 
sphere is divided by the fissures or sulci ; a con- 
volution; a gyre. The gyrl and sulci are complemen- 
tary and mutually definitive. They are most numerous and 
best marked in the brain of the higher mammals (which are 
therefore called gyrencephalous\ and especially in that of 
man. Every gyrus in man has its own name ; but several 
different systems of naming are in vogue, and the nomen- 
clature ia still shifting. The attempt to identify the hu- 
Fig. 1 
Gyri, or Convolutions. 
Fig 
zee, 
Pig. I, brain of rabbit ; fig. a, brain of pig ; fig. 3, brain of chhnpan- 
e, showing si<U- view of the principal or fundamental gyri and sulci 
the mammalian brain. Ol, olfactory lobe ; A, B, C, frontal, oc- 
cipital, and temporal lobes : C 1 , a portion of temporal lobe which en- 
larges until it hides C in fig. 3 ; Sy, Sylvian fissure ; /*, insula or 
island of Reil : SOr, supra-orbital gyrus ; SF, MF, IF, superior, mid- 
dle, and inferior frontal gyri ; AP, PP. anterior and posterior parie- 
tal gyri ; R, fissure of Rolando ; PPl, posteroparietal lobule ; OPf, 
occipitotemporal sulcus ; An, angular gyrus; 2, 3. 4, annectent gyri; 
A T, MT, PT, the anterior, middle, and posterior temporal gyri ; 
SOf, MOc, lOc, the superior, middle, and inferior occipital gyri. 
( Fig. I is a lissencephalous brain ; figs, t and 3 are gyrencephalous. } 
See also the cuts under brain. 
man gyri and sulci with those of other mammals encounters 
difficulties which have thus far been insurmountable ex- 
cept in the cases of the most constant and best-marked 
folds and fissures. (8ee the cuts.) Additional difficulty is 
encountered in the fact that different human brains vary 
in details of the gyri, and the same brain may differ on 
its opposite sides. The principal gyri are noted in the 
phrases below. The gyri represent an enormous increase 
in quantity of the gray cortical matter or cortex of the 
brain in comparison with the actual superficies of the 
cerebral hemispheres, some of the folds being separated 
by fissures an inch or more in depth, and containing three 
layers of gray matter with three layers of white. The gyri 
are to some extent an indication of intellectual power, and 
are better marked when the mental powers of the indi- 
vidual are at their height than in infancy and senility. 
The distinction between gyrus and lobe or lobule, as ap- 
2670 
plied to lesser divisions of the surface of the brain, is not 
always preserved. Gyrus is exactly synonymous with con- 
volution. Angular gyrus, a certain gyrus of the hemi- 
sphere of the Drain in man and monkeys. In man it is 
the short gyrus arching over the upper extremity of the 
superior temporal fissure, the hindmost one of four parietal 
gyri, separated by a short vertical sulcuB from the supra- 
marginal gyrus. See fig, 3, and cut under cerebral. An- 
nectent gyrus, ^ small or secondary fold, which may con- 
nect larger or primary convolutions : especially applied 
to several such gyri of the occipital lobe, as those forming 
the connections of the cuneus or occipital lobule. See 
cut under cerebral. Arched gyrl, four arched convolu- 
tions regularly arranged, in some carnivorous animals, as 
the dog and wolf, beginning with one which borders the 
Sylvian fissure and ending with one which forms the mar- 
gin of the cerebral hemisphere. They are enumerated from 
first to fourth, as by Leuret, or in reverse order (Ferrier), 
or only three are recognized (Flower), when they are also 
called inferior, middle, and superior (Mivart). Ascend- 
ing frontal gyrus, the gyrus bounding the fissure of 
Rolando in front. Also called the anterior central gyrus 
and transverse frontal gyrus. See cut under cerebral, 
Ascending parietal gyrus, the gyrus bounding the fis- 
sure of Rolando behind. Also called the posterior central 
convolution. Callosal gyrus, a convolution of the me- 
dian surface of the cerebrum immediately over the corpus 
callogum and below the callosomarginal fissure. It is con* 
tinuous behind with the gyrus hippocampi, and ends in 
thegyrus uncinatus. Also called convolution of the corpus 
calloaum, &i\A gyrus fornicatus, from its arched or forni- 
cated figure. See cuts under cerebral and tsulcux. Cu- 
neate gyrus, a convolution of the occipital lobe appear- 
ing as a wedge-shaped figure on the median aspect of the 
cerebrum in the fork between theparIetoK>ccinital sulcus 
and the calcarine sulcus. Also called occipital lobule and 
cuneu*. See cut under cerebral. External orbital gy- 
rus, that part of the orbital surface which lies outside of 
the triradiate sulcus. Gray. Frontal gyri, three gyri 
which compose the superior and lateral surface of the fron- 
tal lobe of the cerebrum, all lying in front of the ascend- 
ing frontal gyrus. They are defined by the superior and 
inferior frontal sulci, and by the vertical fissure or pre- 
central sulcus. Gyrus fornicatus. Same as calloml 
fjyrus. Gyrus quadratus, the quadrate gyrus. Hip- 
pocampal gyrus, the continuation of the gyrus forni- 
catus wnere ft dips down behind and below the corpus 
callosum t and continues forward to the uncinate gyrus: so 
called from its relation to the hippocampus. Marginal 
gyrus. (a) That part of the first frontal convolution which 
appears on the median side of the hemisphere. See cut 
under cerebral. (6) The gyrus which arches over the ex- 
tremity of the fissure of Sylvius. See sulcus. Occipital 
gyri, three principal convolutions of the occipital lobe of 
i In- cerebrum, separated by two small transverse sulci, and 
distinguished SB first, second, and ttdrd, from above down- 
ward, or, as in fig. 3, ntperior, middle, and inferior. See 
cut under cerebral. Orbital gyri, the gyri or convolu- 
tions upon the under or orbital surface of the frontal lobe 
of the cerebrum, which rest upon the orbital plate of the 
frontal bone. They are three in number, directly contin- 
uous with and corresponding to the frontal gyri. The two 
best-marked orbital gyri are sometimes distinguished as the 
internal and external. Parietal gyri, four well-marked 
convolutions upon the superior and lateral surface of the 
parietal lobe; and especially two of these distinguished 
as the ascending parietal (or posterior central) and the 
superior parietal, the other two being commonly known 
as the sttpramarffinal and the angular gyrus. (See other 
phrases.) In fig. 3, the superior parietal is called postero- 
parietal lobule. Quadrate gyTUS, a convolution of 
somewhat square figure appearing on the median surface 
of the cerebrum between the callosomarginal Bulcus in 
front and the parieto-occipltal sulcus behind, and contin- 
uous below with the gyrus fornicatus. Also called quad- 
rate lobule and precuneus. See cut under cerebral. Sig- 
moid gyrus, the somewhat S-shaped fold which curves 
about the lateral end of the cruciate fissure, and whose 
surface includes several constant and well-marked "mo- 
tor areas": used especially by English writers. Tem- 
poral gyrl, in fig. 3, a general name of the temporal con- 
volutions : usually in human anatomy more fully called 
temporosphenoidal gyri. Uncinate gyrus. a convolu- 
tion which appears on the median surface of the cerebrum 
nearly opposite the beginning of the gyrus fornicatus. It 
is so called from its shape, and the hook is known as the 
crotchet or uncus. See cut under cerebral. 
gyset, and t*. See guise. 
gyst 1 f, w. A Middle English form of guest. 
gyves 
gyst 2 t, n. An obsolete form of gist, now joist. 
gyst 3 t, 11- An obsolete form of gesft. 
gyst-ale, n. [Appar. < gysfl-, obs. var. of gui'nt, 
+ ale; but appar. also associated with guise, 
with allusion to festive mummery.] See the 
extract. 
In Lancashire, we find the term Gyst-ale, which seems 
to be one of the corruptions of disguising, as applied to 
mumming, and in this sense the entire name, Gyst-ale, is 
confirmatory of Mr. Deuce's observations. Gyst-ale or 
guising, says Mr. Baines, was celebrated in Eccles with 
much rustic splendor at the termination of the marling 
season, when the villagers, with a king at their head, 
walked in procession with garlands, to which silver plate 
was attached, which was contributed by the principal 
gentry in the neighbourhood. 
Hampson, Medii .r-'vi Kalendarium, I. 283. 
gyte 1 (git), a. [Origin unknown.] Crazy; ec- 
static; senselessly extravagant; delirious; dis- 
tracted. Also gite. [Scotch.] 
What between courts o' law and courts u' state, and 
upper and under parliaments, . . . here and in London, 
the gudeman's gane clean gyte. 
Scott, Heart of Mid-Lothian, xxiv. 
There's nae soberer man than me in my ordnar ; but 
when I hear the wind blaw in my lug, it's my belief that 
I gang gyte. R. L. Stevenson, Merry Men. 
gyte'-' (git), n. [Another form of gait, gayt, etc., 
for gey-, n., offspring, a child: see geft, .] 1. 
A child: generally in contempt. 2. A first 
year's pupil in the High School of Edinburgh. 
[Scotch in both senses.] 
gytrash (gi'trash), . [Origin obscure.] A 
spirit or ghost. [Prov. Eng.] 
I remembered certain of Bessie's tales, wherein figured 
a North-of-England spirit called a "Gytrash"; which, in 
the form of horse, mule, or large dog, haunted solitary 
ways, and sometimes came upon belated travellers. . . . 
Close down by the hazel stems glided a great dog, whose 
black and white color made him a distinct object against 
the trees. It was exactly one mask of Bessie's Gytrash 
a lion-like creature with long hair and a huge head. 
Charlotte Bronte, Jane Eyre, xll. 
gyve (jiv), v. t. ; pret. and pp. gyved, ppr. gyving. 
[Also written give; < ME. given, gyren, fetter, < 
gyres, gives, pi., fetters: see gyves.'] To fetter; 
shackle; chain; manacle. [Poetic or archaic.] 
I will -///fv thee in thine own courtship. 
Shak., Othello, U. 1. 
She had gyved 
Them so In chains of darkness, as no might 
Should loose them thence. 
/.'. Jonson, Masque of Beauty. 
One hair of thine more vigour doth retain 
To bind thy foe, than any iron chain : 
Who might be gyv'd in such a golden string, 
Would not be captive, though he were a king. 
Drayton, Black Prince to Countess of Salisbury. 
gyves (jivz), ti. pi. [Also written gives; < ME. 
gyres, gives, pi., fetters; of Celtic origin: cf. 
W. gefyn, a fetter; Ir. geimlieal, geibheal, get- 
bhionn, chains, gyves, fetters, restraint, bond- 
age, perhaps < geibJiim, I take, get, obtain, find, 
receive; cf.gabhaim, I take, receive.] Shackles, 
usually for the legs; fetters. [Poetic or ar- 
chaic.] 
With feteres ant with gyves i chot he wes to-drowe. 
Execution of Sir Simon Fraser (Child's Ballads, VI. 281). 
I thought 
Gyves and the mill had tamed thee. 
Hilton, S. A., 1. 1093. 
Two stern-faced men set out from Lynn, 
Through the cold and heavy mist ; 
And Eugene Aram walked between, 
With gyves upon his wrist. 
Hood, Dream of Eugene Aram. 
= Syn. Manacle, Fetter, etc. See shackle, n. 
