418 
or 1: 8:: 120 + 12%: 1936 : = the force re- 
sisted or employed by the glutei muscles. 
Rvostus:2:y, 
or 1: 6: : 23223: 1936 : =—* the power exerted 
by the quadratus femoris; 
Lkd:dp::s:1* 
or 1:33: 720: 2160. The last proportion gives 
the force exerted by the gastrocnemius and 
soleus muscles to sustain the weight of the man 
together with the weight r ; now as the sum of 
. the forces exerted by the muscles f-+- y + / 
= 2 x (1936) + 2160 = 6032, and the 
Weight supported being only 120lbs., it follows 
that the extensor muscles of the leg, to sustain 
this weight, exert a force = 6032lbs., being 
more than fifty times the weight. 
Force of muscles at various stages of their 
contraction.—The variations which the force 
of muscles undergoes in different states of their 
contraction have not yet been thoroughly in- 
vestigated; though it is a subject not only 
susceptible of being pretty accurately deter- 
mined, but also leads us to form a more cor- 
rect hypothesis of the laws which regulate the 
contraction of the muscular fibres, and of the 
physical operation of the vital agents which 
are the immediate causes of the contraction. 
The force of muscles, according to the ex- 
riments of Schwann, increases with their 
ength, and vice versd. His experiments were 
made on the gastrocnemius muscle of a frog. 
The apparatus which he employed consisted 
of a Saat. to which the frog was fixed, 
with the thigh in the horizontal position, the 
leg being raised so as to be perpendicular to 
the board, and the foot again flexed to the 
horizontal position, in which posture the limb 
was firmly fixed; a rod or beam was suspended 
over the board and made capable of turning 
upon it as its axis of oscillation. This balance 
beam was unequally divided with respect to its 
axis of motion, one arm being to the other as 
1 to 6. To the longest arm of the beam a 
scale was separated; to the other arm the tendo 
Achillis (which had been carefully exposed 
and detached from the heel) was attached by 
means of a thread; by this method a very 
small contraction of the muscle caused the 
other end of the beam to revolve through a 
much greater space, so that the slightest con- 
traction of the muscle became very apparent. 
The ischiatic nerve was then laid bare, cut 
through high up in the thigh, and drawn out, 
great care being taken not to injure the sur- 
rounding vessels. The nerve was then laid 
upon two wires, connected with a galvanic 
battery, consisting of a single pair of plates, 
one of the wires being connected with one pole 
of the battery, and the other made to commu- 
nicate with the opposite pole by using a slight 
pressure upon it. The skin was left entire, 
except where the tendon and nerve were ex- 
posed. By this simple apparatus, Schwann 
observed that the force of the muscle was at a 
maximum when at its greatest elongation, and 
* This computation differs from that in the 53d 
prop. of Borelli where he has substituted new 
and arbi values for s and z in the two last aa 
portions, which diminish the values of y and 
MOTION. 
at a minimum at its greatest contraction. In 
a series of five experiments, which were repeated 
at equal intervals, the forces of the muscles at 
different lengths were in the following propor- 
tions : — 
No. of Muscle. Comparative 
, uscle Difference 
Spotl in grains length of in 
ments. weight Muscle. length. . 
Ove sees e+. 14.1 
60 eereeee .17.1 ocebae ween 
a 120 eek oe mel Ger “eee eo 
180.. Pree. seokiit 
" 0 end of experiment. " 
©. cies cmadea kee 
2 ORE 
‘ 900.2 we oc 0020.4, eden 
0 end of exp. 14.4 
0... ccwdep sce Our 
*etee vcee 18-040 sane 
00 0:0 0208s cane n ee 
50 Saeevecca eke 
0 end of exp. 14.1 
0. ccccceese laws naan eee ‘Z 
4. ; 100. ceecceee IDL. cecccccncten 
200... eeeee ee 2de2 
100. ... ee0+--16.8 
0 eee eee ood kaeke ose age ae 
5 100 . + ec cee ohGsku soe See 
‘ 200...... 2000187 
100... .eesece 16.1 
Qeecseees » 11.17 
This table shows that twice the com ive 
length coincides with twice the force of the 
muscle, and that at its greatest contraction the 
force = 0. In the first two experiments the 
increase of force and length of muscle were 
uniform ; but in the last three the ratios of the . 
force and the length varied; the earliest ex- 
periment, however, was performed when the 
animal might be supposed to be nearest to 
its normal condition, and therefore when the re- 
sult approximated most nearly to the healthy 
play of the muscle. 
These experiments of Schwann are d 
to the hypotheses of Prevostand Dumas, as well 
as to those of Meissner, who the pheno- — 
mena of muscular contraction to be due to the 
force of electric attraction, but as the latter in- 
creases in force the more nearly the attracted bo- 
dies approach each other, and decreases as they 
recede in the inverse ratio of the square of the 
distance, and as the force of elastic bodies” 
varies in a ratio differing from that of muscles, 
when their length and force affecting them 
vary, we conclude that the contraction of — 
muscles does not depend upon any of the — 
known laws connected either with electro- 
dynamics or the forces regulating the molecules — 
of elastic matter. a 
If we conclude from the experiments of 
Bergolotti, Mayo, and Prevost and Dumas, 
that the contraction of muscles is unaccom-— 
panied by a diminution of bulk, and that the 
aggregate molecules present equal volumes ar 
are at equal distances from each other, 
ther contracted or not, the electric force would 
remain constant, whilst the muscular foree 
varied; or if with Professors Gruithuisen and 
