94. The heart is well known to beat after death, if death be not the result of a gradual decay. Sometimes, indeed, its muscular irritability is so active that the heart will beat for hours. E. Rousseau observed it beating in a woman twenty-seven hours after she had been guillotined.[123] Not only will it beat after death, but in many animals even after removal from the body: the heart of a young puppy, or kitten, will beat for three or four hours after its removal; that of a full-grown dog, or cat, not one hour; whereas the beating of that of a tortoise, or a frog, will, under proper precautions, be preserved for days--and even after it has stopped, it may be stimulated to fresh pulsations. Physiologists explain this spontaneous movement of the heart as due to the ganglia in its substance. This explanation, which is founded on what I cannot but regard as a purely imaginary view of the functions of ganglionic cells, must stand or fall with that hypothesis. A long and arduous investigation has led me to doubt whether in _any_ case the heart’s movements are primarily due to its ganglia; at all events, the same spontaneous movements are observed in the hearts of molluscs and crustaceans, which are without even a trace of ganglia; and in the hearts of mammalian embryos long before ganglia or nerve-fibres make their appearance. Not less certain is it that movements of contraction and dilatation are produced in the blood-vessels independently of all central influence. This has been decisively proved by the Italian physiologist, Mosso, when experimenting on an organ isolated from the organism; and although the vessels have their nerve cells and fibres, he justly doubts whether it is to these that the stimulation is due, because the phenomena are observed after the nervous vitality has disappeared. Goltz severed all the tissues in the leg of a rabbit, so that the only connection of the leg with the rest of the body was through the crural vein and artery, which kept up the circulation; yet although the nerves of the skin were thus separated from their centre, so that no sensation could be produced by stimulating the skin of the leg, consequently no reflex from the centre on the vessels, Goltz found that a marked reddening of the skin from congestion of the capillaries followed the application of mustard to the skin. Physiologists who believe that the constriction and dilatation of blood-vessels are due to the action of the ganglionic cells distributed over the walls of the vessels will explain Goltz’s observation as a case of reflex action; but those who agree with me that such an hypothesis respecting the part played by the cells is untenable, will class the observation among other cases of direct stimulation.