1805.] 
tally deflroyed, coldnefs and infenfibility 
take place. and finally the beart concludes 
its motions, end the mu'cles ceafe to be 
irritable, It is worthy of remark that a 
confined air, and a confined refpiration, 
ever precede thefe phenomena, the animal 
‘etires. from the open atmofphere, his 
mouth and noltrils are brought into con- 
tact with his cheft, and envelloped in fur ; 
the limbs become rigid and the blood ne- 
ver coagulates during the dormant ftate. 
On being roufed, the animal yawns, the 
refpirations are fluttering, the heart acts 
flowly and irregularly, he begins to ftretch 
out his limbs, and proceeds in queft of 
food. During this dormancy, the animal 
may be frozen, without the deftruéction of 
the mafcular irritability, and this always 
happens to the garden fnail, and to the 
chryfalides of many infects during the win- 
ter of this climate. 
** The lofs of motion and fenfation from 
the influence of lower temperature ac- 
company each other, and the capillaries of 
the vafculay fyftem appear to be contra&ed 
by the lois of animal heat, as in the ex- 
amples of numbnefs from cold. Whether 
the ceflation of mufcular aétion be owing 
to the impeded influence of the nerves, or 
to the lowered temperature of the mufcles 
themfelves, is doubtful; but the known 
influence of cold upon the fenforial fytem 
rather favours the fuppofition that a cer- 
tain temperature is neceflary for the tranf- 
miffion of nervous influence, as well as 
fenfation.”” 
From other experiments recorded by 
Mr. Carlifle, it appears that the irritabt- 
lity of the heart is infeparably connected 
with refpiration, and that, according tothe 
nature of the inhaled gas, the actions of 
the heart arealtered or fufpended, and the 
whole muicular and fenforial fy(tems par- 
take of the diforder. The blood appears - 
to be the medium of conveying heat to the 
different parts of the body, and the changes 
of animal temperature are connected with 
the degree of rapidity of the circulation. 
Tn confidering the caufes which occafion 
the lofs of mufcular irritability, we are re- 
ferred to workmen whofe hands are expofed 
to the contaé of white lead, the torpidity 
-of whole mufcles feems to be decidedly lo- 
cal, becaule, in many imftances, neither 
the brain, nor the other members, partake 
oi the diforder ; and it generally affects the 
right hand. A chemift has trequently 
experienced fpafms and rigidity in the muf- 
cles ot his fore arms, from the effufions of 
nitric acid over the cuticle of the hand and 
arm. The ufe of mercury occafionally 
Proceedings of Learned Societies. 
479 
brings on a fimilar rigidity in the maffeter 
miuicles. 
A ‘maller quantity of blood flows 
through a mufcle during the ftate of-con- 
traction, than during the quiefcent fate, 
as is evinced by the pale colour of the 
red mufcles when contracted. But when 
the mulcles are vigoroufly con'racted, theic 
fenfibility to pain is nearly deftroyed : this 
mean is employed by jugglers, for the pur- 
pole of fuffering pins to be thruft mto the 
calf of the leg, and cther mulcular parts, 
with impunity. 
The human mofcles are fulceptible of 
changes from. extraordinary occurrences of 
fenfible imprefhons. Long attention to in. 
terefting vifible objects, or to audible fen~ 
fations, exhaufts mufcular ttreneth ; intenfe 
thought and anxiety weaken the mufcular 
powers, and the pafiions of orief and fear 
produce the fame effeet fuddenly, while the 
contrary feelings give more than ordinary 
vizour. To conclude, there are two ftates 
of the mufceles ; one adfive or that of con- 
traction, the other a ftate of ordinary tone, 
which may be confidered as pafi'we, as far 
as relates to the mind; but the nervous 
power feems never to be quiefcent, as it 
re{pects either the volantary or involuntary 
mufcles, during life. The yielding of the 
{phingters appears to depend on their be- 
ing overpowered by antagonift mufcles 
rather than on voluntary relaxation. 
We learn through the medium of the 
Royal Society, that Dr. HERSCHEL has been 
making a feries of experiments to afcertain 
how far telefcopes will enable us to deter- 
mine very fall angles, and to diflinguith 
the real from theYpurious diameters of ob- 
jects: the refult of whichis: 4x. Fhat 
a ten-feet reflector will thow fpurious or 
real difks when their diameter is one fourth 
of a fecond of a degree, which diameter, 
under favourable circumitances may be 
perceived fo diftingtly, that it can be di- 
vided by eftimation into two or three parts. 
2, A difk of one fourth of a fecond in di- 
ameter, to be feen well-defined, requires a 
magnifying power of five or fx hundred, 
3. A real difk of half a fecond in diame- 
ter, may be diftinguifhed from an equal 
{purious one, the latter not being affected 
by power in the fame propurticn as the for. 
mer. 4. The different effets of the in- 
fide and outfide rays of a mirror, are crite. 
ria that fhew whether it is real or {puriois. 
5. When ditks aré lefs than one-fourth of 
a fecond in diameter, they cannot be dif- 
tinguifhed from each other. 
Dr. Herfchel was appiied thefe experi- 
ments and obfervations to the celeftial body 
