The Effects of Electric Shock and Fatigue
on Post-mortem Changes in Muscle"·

BYTADASHI .NAKAI and HOKOTO ONO(This was reported in Japanese on pp. 358-362, Vol. 71, Journalof the Pharmaceutical Society of Japan (1951).)

This experiment was made with use of albino-rats, as a preliminary
test for learning the effects of electrocuting method upon post-mortem
freshness of whale carcass, which Japanese whalers are now making
trial of. The electrocuting method is a method which gives electricalshock to a whale through a harpoon shot into its body in order to kill itin a short time. When this method is used, there is no longer struggle
before death such as· seen in the hitherto used method. It is anoriginal purpose to learn the effect of this struggle and electric shockupon the post-mortem freshness of whale carcass. In order to getsome key authors made an experiment with use of albino-rats insteadof whale body.
They have to thank Dr. T. Maruyama and Prof. Dr. S. Akiya for
their kind guidance and Mr. T. Murata for affording facilities in theexperiment.
MethodMethod to give rats fatigue.
Rats were forced to swim for one hour in an enamelled cylindricaltank about 37 cm in diameter and in depth, at about 37°C.
1.

How to kill them.
To electrocute rats, alternating current of 50 cycles was sent for
about one minute into the tank filled with water with copper plates
as electrodes. As mechanical shock, rats were heavily struck on theirheads with a wooden hammer.
2.

Sampling.
After a certain hours' storage of five albino-rats carcasses, eachabout 120 g. in body weight, in an incubator at 37°C, the same
quantity of muscle was sampled out of hind leg of each rat for thefollowing observations.
3.

* Qhemical studies on frEtshrwss of whale meat. V,

T. NAKAI and H. ONO

178

4. Measurement of pH.
Sample was brayed with a small amount of sea sand in the mortar
and mixed with distilled water four times as much as the sample andits pH was electrically measured with antimony electrode.
Measurement of the amount of amino-nitrogen and volatile basicnitrogen.
10 g. of sample with some sea sand was well brayed in themortar and mixed with 30 cc of distilled water. · After 15 minutes'
heating in the steam-kettle, supernatant was separated by a centrifuge
and the residue was washed again and again with warm distilled water,of which the above supernatant was made to 100 cc. 1 cc of phenolphthalein solution, 20 cc of 10 o/o BaCl2 and by 5 cc excess of saturated
Ba(OH) 2 solution enough to neutralize the mixture were added to 50 ccof the above solution to precipitate phosphate and carbonate, and thenthrough vacuum distillation at 45°C volatile base was collected in 0.02
n-H$04. Excess of the acid was titrated back with 0.02 n-NaOH todetermine volatile basic nitrogen. The distilled water was added so
as to make the remnants 100 cc. Amino-nitrogen was determined bySorensen's formol titration with 50 cc of the filtrate.

5.

6. Measurement of number of. bacteria.
All treatments were aseptically done. With some emery powder
the sample was well brayed. Then the physiological salt solution
diluted it and the number of bacteria was counted in the ordinaryway.
7.

Lactic acid determination.
The sample was treated by Tanaka and Endo's method 0 to get atesting solution and lactic acid in it was determined by Friedemannand co-workers' method. 2 >Results obtained
L

Comparative study of post-mortem changes in muscle
between normal and fatigued rats electrocuted.

As see in Table I, both groups showed the lowest pH from 12thto 18th hour after death. Normal group showed always more acidthan fatigued one.
Although small till 12th hour, the amount of volatile basic nitrogenwas suddenly increased after that time. Till 12th hour there wasEffects of Electric Shock and Fatigue on Post-mortem Changes in Muscle

179Tobie I. Elec1ocution.
Lapseof timeafterdeath(hrs.)
06
1218II

24II

Fatigued*

Normal*

**
pH
6.4
5.9
5.8
5.7
5.7
6.2
6.4

Volatile
Volatile
Number of
Number of** basic N. Amino N. bacteria
basic N. Amino N. bacteriapH(mg/100 g) (mg/100 g) (in 1_ID_(mg/lOOg) (mg/100 g) (in 1 g)
12.6
13.0
15.9
28.9
52.8
107.9
143.6

51.9
53.6
68.4
86.8
114.4
186.2
245.9

00
170
560
740
166.4xl03***
countless

6.7
6.5
6.1
6.0
6.2
6.3
ti.6

12.4
13.2
16.3
21.6
40.0
132.0
114.8

53.0
61.8
71.9
103.8
110.8
193.4
184.0

001302720
432027695 xl03***
countless

Intensity of electric current through the water-tank:-. Normal group-96100 V, 77-79mA; Fatigued group-96-lOOV, about 160mA (because water inthe tank was soiled with excrement). Carcasses were kept at 37°C.
* Every time 5 rats of each group were used for measuring.
** 'About an hour passed from their dissection to measurment.
*** It was macroscopically obvious that there were more bacteria in thefatigued group than in the normal group, though impossible to accountfor them.

little difference between two groups, while at 18th hour, normal group
showed larger amount of volatile basic nitrogen than fatigued one asseen in two instances. At 24th hour, there was no clear trend.
As for amino-nitrogen, till 12th hour a little larger amount of it
was found in fatigued group and then it became irregular.
Bacteria were remarkably numerous in number in fatigued group.
No special feature was found by macroscopic observation of rat
carcass tiil 6th hour. At 12th hour rather with offensive smell, gas
generated in its intestine and swelled the abdomen. The difference
between two groups was difficult to find. At 18th hour, both groups
gave out a putrid smell and their muscle increased its viscosity anddegree of grey colour and lost its elasticity. In both instances, however, fatigued group was seemingly better than normal group andkept still slight reddish colour and exudation on the side of carcasson the floor was never found or a little less than the normal group.
At 24th hour, in the first experiment, the apparent difference between
two groups was difficult to find. While, in the second one the fatigued
group was distinctly better.
In short, in comparison between two groups on post-mortem
changes, the results of comparison of macroscopic state of putrefaction

T. NAKAI and H. ONO

180agreed quite well with that of the amount of volatile basic nitrogenbut not with that of the number of bacteria. From pH and the numberof bacteria, it was naturally expected that macroscopic putridity appearedstronger in fatigued group than normal one but the truth was not so.
It is, however, too premature to draw the conclusion, for only a few
experiments were made.
Rigor mortis observed in all experiments will be mentioned later.
II.

Comparative study between normal and fatigued
rats killed by mechanical shock.
Table II. · Ceating to death.
I

Lapse of time iafter death i(hrs.)

Normal*pH**IVola tile basic I Amino N.
N.
(mg/lOOg)(mg/100 g)

6.9
5.9
6.0
6.2

0
1218
JI

Fatigued*

13.8
19.6
75.0
110.0

57.2
80.2
156.7
166.0

pH

** Volatile basic
N.
(mg/100 g)

6.8
6.1
6.5
6.8

12.3
19.4
34.8132.8

Amino N.
(mg/100 g)
60.1
82.5
138.5
188.5

* Same as in Table. I. ** 30~40 minutes passed from their dissection tori:teasurment. Carcasses were kept at 37°0.

As for pH, in both groups, at 18th hour already the turn towards
alkalinity was found. Initially in the normal group, it was nearer
neutral than the fatigued group and then it changed to more acidside. The increasing ratio of pH was rather smaller in the normalgroup than the fatigued group. This was probably due to the factthat the normal group contained larger amount of glycogen, so lactic
acid was made more abundant in post-mortem glycolysis than thefatigued one. The amounts of volatile basic nitrogen and aminonitrogen suddenly increased at 18th hour as seen in Exp. I. No definite
difference could be, ho.wever, found between these two groups. As statedin I, comparison of the amount of volati1!3 basic nitrogen agreed always
with that of degree of rottenness in macroscopic observation.
III.

Comparison between electric and mechanicalshocks as method to kill normal rats.

As seen in Table III, the initial pH was in far more acid side inelectrically shocked group than in mechanically shocked one. At 12thhour and 18th hour, their pH were approximately equal.

Effects of Electric Shock and Fatigue on Post-mortem Changes in Muscle

181

Table III.
i

Lapse of time iafter death !
(hrs.)

Electrocution *Beating to death***'Volatile basic[ Amino N.
pH /N.
(mg/100 g)' (mg/100 g)**!Volatile basici Amino N.
pH 'N.
! (mg/100 g) / (mg/100 g)
6.9
12.3
57.2
5.9
24.3
81.9
I
6.1
134.1
238.2
!

I6.3
5.9
6.0

0
1218

12.3
19.555.1

II

54.9
76.1
123.3

IiI
I

* and ** same as in Table II. Carcasses were kept at 37°0.

The volatile basic nitrogen and amino-nitrogen increased theiramounts faster in mechanically shocked group than in electrocutedgroup. The comparative results between I and II can make it clear.
This agreed with the result of macroscopic observation. Namely the ,mechanically shocked group was decomposed earlier than the electrocuted one.
This is probably due to heavy bruise on the head and to thechange of pH in muscle to acid side through electric shock (Confer IV).
IV.

pH change of muscle through electric shock.

( a) Comparison between normal and fatigued conditions.
In the above experiments, normal rats electrocuted gave smaller
pH in muscle than fatigued,_ electrocuted rats and normal, mechanicallyshocked ones. It is in general, however, that fatigued muscle showes
more acid than not fatigued one. So the above result was probably
due to the electric shock. This experiment was carried on for the
purpose of assurance of it.
fn order to measure pH as soon as possible after death, thesample, without braying, was closely attached to the electrodes in theshape of chop. About 5 minutes passed from death to measurement.
Sample was obtained from the same part of hind leg as in the previous experiments.
Forced to swim in the above mentioned tank, rats were throwninto a small tank full of clean water and charged with alternating
current. They were fatigued rats. Normal rats were directly throwninto the smaII tank. The current intensity was, therefore, different
from that of the above experiments.
Probably due' to the chop used, sensibility of the pH-meter wasso bad and unconstant that it was difficult to measure pH with it.
It could be affirmed, howeve:r;, that electric shock changed pH in muscle

182

T. NAKAI and H. ONO

Table IV.
Normal, Electrocuted-8e~w~~n~~li--m

I

mIfff
m160
185

I!

90
75
75
120

- - - ·--··--

6.4
6.2

m

6.6
6.7
6.7
6.7

f

--~---- --Normal, Beaten

Fatigued, Electrocuted
Sexmf\ Weight
pH
Sex I Weight__(=g)~----- - - (g)
i 175
6.9f
I 120
215
7.0f
220
90
7.0f80757.5f80
180
II80

l

1I! I 1~~~::~____ _J_ _______'~-

pH
7.1
6.9
7.5
7.4
7.3
6.8

---~-----to acid side and normal rats showed smaller value in pH than fatigued
one.

( b) Ejfeet of eleetrie current upon pH of musele eut off.
After the normal rats were killed by mechanical shock, muscle ofone side of their hind legs was cut off and it was hung in the water
charged with the alternating current of 95 V and 45 mA for 30 or 60
minutes. Then brayed swiftly and fully with some quantity of sand.
Distilled water four times as much as the sample was added to it
and its pH was measured. For comparison, it was made with the useof the same part of muscle of another leg with no electric current
flown. This result showed that the electric current gave no effectupon pH of muscle which was cut off carcass. So the change in pH
to acid side by electric shock might take place only in the living body.
Table
Lapse of timeafter death(hrs.)
000
12v.

I

Electrifying time(seconds)
1I
30
60
60
6060

pH

pH(control)

7.1
7.0
7.0
6.4
6.1

7.3
7.0
6.8
6.4
6.1

Carcasses were kept at 37°.

( c) Any constant relation between the current intensity, sex, bodyweight and pH change was not found.

lnffects of Electric Shock and Patigue on Post-mortem Changes in Muscle

183

(d)

Cause for pH change•. As the cause for pH change in electrically shocking, the authors
first expected lactic acid and measured the amount of lactic acid of
male rats normal and fatigued which were killed by electric ormechanical shock, instantly after death.
Table VI.
----------·!

Electrocution
Weight(g)NormalIpH175}
200 '6.2110}
110

6.3

Lactic acidI (mg/100 g)

Ii
I~

125.5

Fatigued

6.5125}
135

6.9

i!

B eating to deathiII

84.5

I!

Weight(g)Lactic acid(mg/100 g)

190}
210

52.1

190}
210

75.9

I·i
I,_175}200-77.8

i
I

I

95.0
--

As shown in the above table, the amount of lactic acid ranks asfollows.
normal rats electrically shocked> fatigued rats electricallyshocked > fatigued rats mechanically shocked > normal ratsmechanically shockedConsequently the cause for pH change is nearly sure to lie in thegrowth of lactic acid.
Electric stimulus inspires the muscle and is followed by fatigue.
So the increase of the amount of lactic acid in muscle is naturallyconjectured. Rats are gradually fatigued through swimming and muscle
glycogen is consumed and ·lactic acid accumulates, Grown lactic acidis however not all accumulated but a part of it is gradually excretedeven in the process of fatigue. Now, when electric impulse stimulates
very intensely the muscle of normal and fatigued rats, the formerrats produce the considerable amount of lactic acid in a very shorttime and accumulate all of it without excreting. We can be ready toimagine that the amount is larger than the total amount of lactic acidaccumulated before the electric shock and lactic acid newly produced
through it in the latter. So pH is to be smaller in the former thanin the latter. This is the authors' interpretation for the phenomenon
that pH of the muscle of normal rats is smaller than that of thefatigued rats in electrically shocking.

184T. NAKAI and H. ONO

V.

Rigor mortis.

Rigor mortis observed in the above experiments is summerized asfollows. Carcasses were kept at 37°C.
Table VII.
Electrocution

Appearance (hrs. after death)
Beginning of Loose (hrs. afterdeath)I

Beating to death

NormalI Fatigued

Normal

1-1.5

0.5-1

1.5-2

4-4.5

3.5-4

3.5-4

II

Fatigued
1-2

II

Rigor mortis began earlier and stronger and later got loose inelectrically shocked rats than in the mechanically shocked ones.
Rigor mortis began earlier and got loose earlier in fatigued rats
than in the normal ones.
Resume1. Either through electric shock or through mechanical shock thecondition of rats instantly before death (normal or fatigued) did notgive any definite effect on the post-mortem change of the amounts ofvolatile basic nitrogen and amino-nitrogen. The increasing speed ofthem is however larger in rats mechanically shocked than in the rats
electrocuted. Namely the former rotted faster than the latter. From
this result only, putrefaction seems to depend more on the killing
method than on the condition instantly before death.
2. Number of bacteria on the electrocuted rats was always larger
in fatigued group than in the normal group. The result of the comparison of number of bacteria, however, did not agree with that ofmacroscopic observation. On the contrary; the result of the comparisonof the amount of volatile basic nitrogen agreed quite well with thatof macroscopic observation.
3. In all experiments pH changed swiftly to acid side immediately
after death. When rats were killed by mechanical shock, it began toturn towards alkalinity around 12th hour after death and when electrocuted, it began at 12th to 18th hour. About that time rot increased
its degree. pH moved in more alkaline side in the fatigued groupthan the normal group.
4. The electric shock changed pH of muscle to acid side. In thiscase, pH of muscle of normal group was smaller than that of fatigued

Effects of Electric Shock and Fatigue on Post-mortem Changes in Muscie

185group. This is probably due to the sudden rise of the amount of lactic
acid caused by sudden and intense stimulus by electric shock.
5. Rigor mortis lasted longer and stronger in the electrocutedgroup than in the mechanically shocked group.
Literatures1) Biochem. z., 210, 120 (1929).
2) J. Biol. Chem. 73, 335 (1929).