FURTHER REMARKS ON THE MAMMALIAN SPINAL PREPARA-
TION. By H. E. ROAF and C. S. SHERRINGTON (Physiology
Laboratory, University of Liverpool).
(Received for publication 18th March 1910.)
A DESCRIPTION was given1 a year ago of a way in which the headless
carcass of a freshly killed mammal may through several hours be utilised
for various laboratory purposes, including those of instruction. Regular
class-work with such preparations during the past year has confirmed
the favourable experience of their resistance, and somewhat extended our
acquaintance with their possibilities. Beyond the experiments mentioned
in the previous paper, others have now been tried and found suitable for
class-work with the preparation. Among these have been examination of
the movements of the larynx, excited by faradic stimulation of the recurrent
laryngeal and superior laryngeal nerves; observation of the pilomotor
effects of various parts of the sympathetic; the change in volume and
colour of the kidney under stimulation of nerves accompanying the renal
vessels; contraction of the urinary bladder on stimulation of its nerves;
and the effect on arterial blood-pressure of stimulating the distal end of the
cut splanchnic, the cross-section of the cervical spinal cord, and of the
administration of chloroform and ether mixed with the air from the bellows
inflating the lungs.
As to the observations involving arterial blood-pressure, it may be
remarked that these, for class-work, can be made quite effectively with
apparatus of a most inexpensive kind. A piece of glass tubing bent to
U shape, with a short side-piece blown on near the end of the shorter limb,
fastened in front of a flat penny ruler with millimetre markings, serves as
manometer, to be clamped upright in a chemical standard. A threepenny
glass syringe, two feet of ordinary 4 mm. india-rubber tubing, and a glass
cannula complete the requisites. In making connection between manometer
and artery, three thread loops obviate the need for any arterial pincettes;
the most distal, when tied, serves to occlude the vessel and afford a means
of holding it in manipulation; the proximal is not tied, but when the
artery is to be opened is dragged gently to one side sufficiently to occlude
the vessel for the time; the middle loop is tied round the inserted cannula.
The glass syringe serves for filling the tubing and adjusting the pressure
in manometer.
1 Journ. of Physiol., xxxviii. 375, 1909.
Downloaded from Exp Physiol (ep.physoc.org) by guest on November 23, 2011
210 Roaf and Sherrington
Concerning the suitability for class-work of some of the experiments of
which we have made trial with the preparation in the past year, a word of
reference may be welcome.
1. The Bell-Magendie law of the spinal roots.-The roots best
suited are those of the lumbosacral plexus: a line joining the summits of
the iliac crests usually crosses just posterior to the exit of the seventh
lumbar roots from the spinal theca. In preparing the roots, there is likely
to be severe hemorrhage unless the pelvis be raised, leaving the abdominal
and chest movements free in the prone position of the preparation. The
pelvis can be suitably raised on a small hot-water bottle. It is well also,
in making the dissection, to support the vertebral column by holding
a spinous process by a pliers in the left hand while removing the dorsal
arches of more backward vertebras with cutting pliers in the right hand.
During the dissection, chloroform or ether should be administered with the
air from the bellows in order to lessen reflex actions. Or curare can be
given; when this is done the femoral artery of one side is ligated above its
profundar branch in order to keep the curare from one limb. The central
stumps of the nerve-roots can then be examined for reflex effects on blood-
pressure under curare, the peripheral stumps for their direct motor effect on
the limb musculature.
2. Heart-block.-A practically unfailing way of showing heart-block,
and one well suited to class-work, is, with the decapitate preparation, to
intermit the ventilation of the lungs, allowing the onset of an asphyxial
condition of the blood. At a certain stage of asphyxia there ensues, as
shown in the previous paper, an abrupt reduction in the frequency of the
ventricular beat, not due to vagus inhibition. It is in fact due to heart-
block. " From a frequency of 300 per min. it now absolutely abruptly drops
to 150 per min., the amplitude of the manometer oscillations becoming cor-
respondingly increased." 1 The condition is soon relieved by re-connecting
the bellows with the lungs. This induction of and recovery from heart-
block dependent on asphyxial condition of the blood can be repeated
a number of times in succession on the same preparation.
3. Effects of stimulation of the cross-section of the spinal
cord in the anterior cervical region.-In making the preparation the
cross-section of the cord is of necessity exposed, where it lies within the
compass of atlas vertebra. For class-work, excitation of points in this
cross-section can be conveniently carried out by the method of unipolar
faradisation. A copper plate with cotton-wool soaked in strong salt
solution is affixed to a part of one forearm whence the hair has been
removed. This plate is the diffuse electrode; the stigmatic electrode is
of the convenient form described2 by A. Frohlich and one of us in
regard to experiments on the spinal cord. From each lateral half of the
cross-section of the cord, at the exposed level, stimulation excites, according
1 Journ. of Physiol., xxxviii. 375, 1909. 11 Journ. of Physiol., xxviii. 14, 1901.
Downloaded from Exp Physiol (ep.physoc.org) by guest on November 23, 2011
Further Remarks on the Mammalian Spinal Preparation 211
to the point of cord stimulated, the following effects: (1) 1 stepping of the
ipsi-lateral hind limb, often accompanied by harmoniously timed but weaker
stepping of the crossed hind limb, the movement in the two hind limbs
being always of opposite phase; (2)2 the scratch-reflex of the ipsi-lateral
hind limb; (3)3 erection of the hairs of the tail, accompanied by a great
rise of arterial blood-pressure, and by a wagging of the tip of the
tail, such as is seen in a cat in anger. The effect on the hairs is not
confined to one side of the tail.
4. Reflex inhibition of a flexor reflex.4 -The muscle chosen is
sartorius, e.g. in right limb. All the nerves of that limb except the nerve
of the sartorius are severed, and the psoas, pectineus, and tensor fascie
femoris muscles, together with the quadratus femoris and the glutei, are
resected freely from their attachments. In the other hind limb also it
is advisable to sever the main nerve-trunks, namely, sciatic, obturator,
and femoralis. The central stump of an afferent nerve in each limb is then
prepared for excitation by faradisation. The sartorius is now freely
detached from the knee and from its lateral and deep connections, the
nerve and blood-vessels entering high up from the medial side being
carefully preserved. The muscle's distal end is connected with a myo-
graph. Stimulation of the ipsi-lateral afferent nerve-trunk then excites
reflex contraction of the muscle; and while this is in progress, excitation of
the contra-lateral afferent nerve, if strong, produces immediate relaxation of
the sartorius contraction.
1 Sherrington, Journ. of Physiol., xxx. 2 Sherrington, this Journal, iii., 1910.
3 Further observations on this effect are in progress by one of us.
4 Proc. Roy. Soc., B., vol. lxxxi. p. 249,1909.
Downloaded from Exp Physiol (ep.physoc.org) by guest on November 23, 2011