HYDROCARBON  , in

chemistry, a compound of carbon and hydrogen . Many occur in nature in the free state: for example, natural gas, petroleum and paraffin are entirely composed of such bodies; other natural sources are india-rubber, turpentine and certain essential oils . They are also revealed by the spectroscope in stars, comets and the sun . Of artificial productions the most fruitful and important is provided by the destructive or dry distillation of many organic substances; familiar examples are the distillation of coal, which yield's ordinary lighting gas, composed of gaseous hydrocarbons,'and also coal tat, which, on subsenuent fractional distillations, yields many `liquid and C,H5N2Cl + K2SO, = KCI + C,H,N2•SO3K, C6H5N•>•SO3K + 2H = C,H,•NH•NH•SO3K,C5H,N H • NH • SOsK+HCI + H2O = C6H,• NH • N H2' FICI + KHSO1 . Phenylhydrazine is a colourless oily liquid which`rturtis brown on exposure . It boils at 241 ° C., and melts at 17.5° C . It is slightly soluble in water, and is strongly basic, forming well-defined salts with r u acids . uch for For ethe detection of xample as aldehydes and ketones) hc d az lie orbital plates of the frontal bone being inclined forwards give a ~ very important reagent, since des it combines? with enthlhem with a downward' tilt to the eyes, which have also peculiar rolling elimination of water and the formation of well-defined hydrazones movements . The face is small, and this, with the enlarged head, gives 'a remarkable aged expression to the child . The body is ill-noilrished,, the bones are thin, the hair is scanty and fine and the teeth" carious or absent . The average circumference of the adult head'is 22 in., and in the normal child it is of course much less . In chronic hydrocephalus the had of an infant three months old has measured 29 in.; and in the case of the man Cardinal, who died` in Guy's Hospital;' the head 'Measured 33 in .

In such cases the head cannbt be' supported by the

neck, and the patient has to keep mostly in the recumbent posture . The expansibility of the skull prevents destructive pressure on the brain, yet this organ is materially affected by the presence of the fluid . The cerebral ventricles are distended, and the convolutions are flattened . Occasionally the fluid escapes into the cavity of the cranium, which it fills, pressing down the brain to the base of the skull . - As i. consequence, the functions of the brain are interfered with, and the mental condition is impaired . The child is dull, listless and irritable, and sometimes imbecile . The special senses become affected as the disease advances; sight is often lost, as is also hearing . Hydrocephalic children generally sink in a few years; nevertheless there have been instances of persons with this disease living to old age . There are, of course, grades of the affection; and children may present many of the symptoms of it in "a slight degree, and yet recover, the head ceasing to expand, and 'becoming in due coirtse'firmly ossified . Various methods of treatment have been employed, but the results are unsatisfactory . Compression of the head by bandages, and the administration of mercury with the view of promoting absorption of the fluid, are now little resorted to . Tapping the fluid from time to time through one of the spaces between the bones, drawing off a little, and thereafter employing gentle pressure, has been tried, but rarely with benefit .

Attempts have also been made to establish a permanent drainage between the interior of the lateral ventricle and the sub-dural space, itnd between the lumbar region of the spine and the

abdomen, but without satisfactory results . On the whole, the plan of treatment which aims at maintaining the patient's nutrition by appropriate food and tonics is the most rational and successful . (E .