A plethysmograph is a glass cylinder provided with a rubber cuff and with stop cocks and rubber tubes. The subject’s hand is enclosed in the cylinder, the rubber cuff surrounds the arm, and one rubber tube leads to the tambour, a pan covered with sheet rubber, upon which rests a needle. The needle plays upon a revolving drum covered with smoked paper. The plethysmograph and tambour are filled with water, oil, or air, according to the conditions of the experiment. If the size of the hand, as it is enclosed in the cylinder, should increase, the fluid in the cylinder would be pressed into the rubber tube and into the tambour pan. The rubber cover of the tambour pan would be forced up, and this would lift the needle resting upon it. The needle thus writes the record upon the smoked paper. Contract ed muscles occupy a very little less space than relaxed muscles, hence, when the fingers are strongly flexed, while the hand is encased in the plethysmograph, the needle is permitted to fall. But after the muscles are relaxed, the blood flows into the hand in increased amount, and the needle is sent up again, higher than before the muscular contraction. Very slight changes in the amount of blood in the hand and forearm are recorded by this apparatus. The effects of the artificial lesion and of the various stimulating and inhibiting manipulations upon the blood supply to the arms are as follows: Stimulation of the tissues near the roots of the nerves which make up the brachial plexus produced slight effect, and that only after a long latent period, and with an amount of stimulation which occasioned a really painful sensation. It appears from these experiments, that such manipulations were only indirectly effective, probably through the sensory fibers of the brachial plexus and the chief vaso-motor center in the medulla. Stimulating movements applied to the brachial plexus under the clavicle caused a decrease in the blood supply to the arm, evidently by causing the constriction of the arterioles. This manipulation was followed by an increase in the blood supply, beyond that originally present. It appears, then, that the brachial plexus carries the vaso-motor nerves from this point. Anatomically, it is known that the brachial nerves receive gray fibers from the ganglion stellatum. Stimulating manipulations to the tissues near the first second and third thoracic spines caused no perceptible effect upon the blood supply to the arms and hands. Stimulating manipulations to the tissues near the fourth and fifth thoracic spines caused a decreased amount of blood in the hands. This reaction must be due to vaso-motor nerves to the hand. The stimulation of this center is known to cause a constriction of the pulmonary arterioles, and this must raise the blood pressure. The effect produced upon the arterioles of the arm by this manipulation is evidently sufficiently pronounced to overcome the effects of the increased blood pressure. The artificial lesion in the same area causes an increased amount of blood in the hand. This, again, is directly opposite to the effect which is to be expected if the pulmonary vaso-motors were alone active under these circumstances. Stimulating manipulations given to the centers below the sixth thoracic spine caused an increased flow of blood to the hand. The vaso-motors to the hand were evidently not themselves affected by this manipulation. The stimulation of these centers—i.e., below the sixth thoracic spine—causes a constriction of the vessels in the liver and intestines, the systemic blood pressure is thus raised, and the blood flow to unaffected parts of the body is increased. In the same manner, the artificial lesion below the sixth thoracic spine caused a decreased blood flow to the hands. That is, the artificial lesion below the sixth causes a dilatation of the vessels in the liver and intestines, and the blood is mechanically drained away from the other parts of the body, including, of course, the hands and arms. The osteopathic or superficial center for the arterioles of the arms is therefore found near the fourth and fifth thoracic spines. In a number of instances of injury to the hands and fingers, in persons otherwise healthy, there were reflex muscular contractions near the fourth and fifth thoracic spines. Muscular contractions near the origin of the fibers of the brachial plexus were less constant. In some case reports of Raynaud’s disease, Dr. J. L. Adams describes lesions affecting the fourth thoracic vertebra, and he reports favorable results from the correction of these lesions. No
experiments were performed for investigating the centers controlling the
vaso-motors to the legs.
Raynaud’s Disease, any text book of medical practice. Raynaud’s Disease,, McConnell and Teall’s Practice of Osteopathy. Raynaud’s Disease, A. O. A. Case Reports. |