Heubel[66], and later Rosenstein[67], found that, in dogs poisoned with lead, definite cerebral anæmia was produced, due to vaso-constriction, and consider it to be due to the direct action of lead upon the intima of the vessel walls. Associated with such poisoning were symptoms of eclampsia and uræmia, and the latter author considers that the uræmia is due to vaso-constriction of the kidney vessels. Oliver[68] and others have also pointed out the alteration in the pulse-rate associated with exacerbations of colic, and a number of observers have noted that certain drugs, such as atropin and amyl nitrite, which are known vaso-dilators, have a distinctly calming effect upon the paroxysms of pain. One or two other observers have actually noted the presence of hæmorrhages in the lesions; thus, in the case quoted by Mott[69] definite yielding of the vessel walls and signs of old hæmorrhage are described amongst other lesions in the brain. Seifert[70] also describes the presence of hæmorrhages amongst the ganglion cells in the anterior columns of the cord, both in the case of persons who have died of lead poisoning and animals to which lead had been given experimentally. In addition, Sajous[71] describes a case of paralysis of the superior laryngeal nerve, associated with hæmorrhages, in the region of the abductor muscles of the larynx. Mott’s case also showed this laryngeal hæmorrhage. More recently Elschnig[72], in his observations upon the eye, has determined a close association between vaso-motor affections, constrictions, and dilatations, and various eye lesions, such as amaurosis and amblyopia, occurring in lead poisoning. Rambousek[73], in summing up Elschnig’s work, points out how much his observations tend to bridge over the gap between the action of lead upon the blood, the bloodvessels, and the nerves. He points out that the eye is a peculiarly favourable organ for watching the effect of a poison so insidious as lead. The bloodvessels, the nerves, and the muscles, are all open to inspection and actual observation to a degree not to be found in any other part of the body. Elschnig[74], in a typical case of sudden lead amaurosis associated with acute lead colic, found that very definite motor spasm of the vessels of the eye, conjunctiva, and the retina, were associated with the amaurosis. He argues from this that the action of lead is probably directly upon the unstriped muscular fibre of the vessel walls; that such an action may, and does, extend to the vessels of the eye muscles, producing paralysis of the muscles of accommodation, and a dilatation of the pupil, which may be observed in a large number of persons employed in conditions subjecting them to lead absorption. Elschnig further considers that the transitory amaurosis which is often associated with lead poisoning may be due to vaso-motor disturbances in the brain itself, as well as in the eye.