THE CIRCULATION 169 



45. Injuries to the Blood-vessels. It is important for us to 

 be able to discriminate between an artery and a vein, in the 

 case of a wound, and if we remember the physiology of the 

 circulation we may readily do so. For, as we have already 

 seen, hemorrhage from an artery is much more dangerous than 

 that from a vein. The latter tends to 'cease spontaneously 

 after a short time. The arterial blood flows away from the 

 heart with considerable force, in jets, and its color is bright 

 scarlet. The venous blood flows toward the heart from that 

 side of the wound furthest from the heart, its stream being 

 continuous and sluggish; its color is dark. In an injury to 

 an artery, pressure should be made between the heart and the 

 wound, while, in the case of a vein that persistently bleeds, it 

 should be made upon the vessel beyond its point of injury. 



46. Effects of Alcohol upon the Heart. The first symptoms 

 after a moderate dose of alcohol is an increase of the heart's 

 action, a flushing of the face, a sensation of warmth within, a 

 general glow without, and some other appearances of increased 

 vitality. The action has been that of a spur or goad. It has 

 caused strength to be expended instead of increasing it, and, in 

 fact, costs the system whatever amount of force is necessary 

 to expel it ; so that there is a loss of strength, and not a gain. 



15. Assimilation in Repair. "Most animals have the power to 

 repair, to a greater or less extent, the mutilations they undergo. In 

 man, if the skin is torn off, a new skin heals over the injury, and a broken 

 bone is caused to re-unite by the deposit of bone tissue between the frag- 

 ments. But among the lower animals this power is carried to a high 

 degree. The tail of a lizard, if cut off, will quickly form anew, although 

 of a complex structure ; and spiders and crabs are able to develop new 

 claws upon the stumps of broken ones. Observations made on salaman- 

 ders, or water-lizards, show the still more remarkable fact that the eye 

 and a part of the head may be entirely restored. Certain kinds of earth- 

 worms can reproduce a large portion of their bodies, and any fragment of 

 the hydra is able to restore itself, and become a complete creature after its 

 kind. Assimilation is especially active in early years, while the body is 

 growing ; for this reason, among others, the perfect health of children 

 requires that they shall give a greater number of hours to sleep deep, 

 regular, and undisturbed sleep than is needed in later life." Milne 

 Edwards. 



45. What is stated of the injuries to the blood-vessels ? 



46. How does alcohol affect the heart's action ? 



