SCIENTIFIC SUMMARY. 
437 
shown by Schiff that, after section of the anterior roots, all the muscular 
nerves after a while are found in a state of degeneration. The knowledge 
of the position of the limbs may come from the nerves of the tendons and 
of the soft parts about the joints. In a comparatively recent number of the 
Archiv fiir Nervenkrankheiten,” M. Bernhardt describes how he arranged 
some pulleys at the foot of a bed, so that an unseen weight might be raised 
by the hand or foot. The experimenter determined first with what accu- 
racy he could estimate the weight attached to the cord when raised by 
voluntary motions. Then he caused the muscles to contract by electric 
stimulus, and found that, in the absence of a volitional impulse, it was 
much harder to tell how much weight was raised. 
Irritahility of the Heart of the Frog. — The Lens,” in its last number, 
has a short note on this subject. It says of Batrachians generally that 
besides being obliged to pump air down into their own lungs, which 
explains why the gular membrane underneath the under jaw is so elastic, 
acting on the volume of inhaled air in the cavity of the mouth on the 
mechanical principle of bellows, they catch game with the point of the 
tongue, drink through the spongy texture of the skin on the back, and live 
months in succession concealed in the mud bed of a pool without respiring ; 
and yet the systole and diastole, or in plainer words, the contraction and 
expansion of the heart, is not suspended. Their vitality is remarkable,, 
since the small amount of oxygen introduced into the arterial blood when 
making the final plunge in autumn keeps the spark of life alive till emerging 
from the water in the spring. If the heart of a frog is cut from its con- 
nections within the pericardium and placed on a table, it will pulsate and 
throb energetically for some minutes. When apparently quiescent, the 
point of a needle will rouse it again into spasmodic energy. Finally, by the 
touch of irritants, its irritability is completely exhausted. After experi- 
menting full half an hour in that manner, we were struck with the lively 
vaultings of the frog from which the heart had been taken. Certainly it 
was conscious of its relations, for it avoided many cautious attempts to cap- 
ture it on the part of the operator. It was some hours before death closed 
the scene. The vital tenacity of reptiles, particularly batrachians and 
chelonians, which include the tortoise family, is remarkable, and worthy 
of more extended scientific investigation. 
Action of Certain Substances on the Spinal Cord. — The ‘‘ Lancet,” in a late 
nnmber, has an important article on the infiiience of substances on the 
reflex excitability of the cord. It states that Dr. S. Meihuizen gives, in 
Pfliiger’s Archiv ” (Band vii., Heft 4 and 5), the results of a series of experi- 
ments he has made on the effects of various agents on the reflex irritability 
of the spinal cord. The animals were chiefly frogs, and the disturbing in- 
fluence of the brain was removed by section of the cord below the medulla 
oblongata. The test of the degree of irritability of the spinal cord was in 
most instances very dilute (| per cent.) sulphuric acid, which was applied to 
the surface of the skin at intervals of a quarter of an hour, and the time 
before contraction occurred noted. Meihuizen finds that bromide of potas- 
sium rapidly depresses the excitability of the spinal cord, and ultimately 
entirely abolishes it, and he gives certain experiments which show that it is 
not due to the action of this salt on the periphery, or on the nerve cords. 
