HEMATEIX. 



HEMERALOPIA. 



654, 



helmet usually protected the face. Both the helmets found at Cannte, 

 however, protected the face, and have projecting nasals. A helmet 



found at Pompeii (and now in the collection at Goodrich Court) has 

 the nasal projection. Lipsius's treatise ' De Militia Romana" (iii., c. 5), 

 contains a full account of the Roman helmet, with which the reader 

 may compare the plates and descriptions in the third volume of 

 Count de Caylus's ' Recueil d'Antiq.' For the helmets in more modern 

 use, Grose's Treatise ' and Meyrick's ' Critical Account of Ancient 

 Armour ' must be referred to. Among the varieties which had separate 

 names we find the Chapelle de Per, the Bacinet, the Burgonet, the 

 Castle, the Hufken, the Morion, the Salade, and the Skull. These 

 were almost invariably of steel. There was also the Justing Helmet, 

 used in tournaments, which wag sometimes of leather. 



, Morion ; *, Burgonet ; of the time of James I. 



The natal, the vmtaile or movetible front, the vigor, lifted up by 

 pivots, and the bevor, to allow of drinking, were the names of parts 

 of certain helmets introduced at different period*, and not always 

 used. 



As ornaments over the shield or coat of arms, helmets are still used 

 in hrraldry. The full-faced helmet with six bars, all of gold, damasked, 

 is for the sovereign and princes of the blood ; the fall-faced helmet of 

 steel for marquises and dukes; earls, viscounts, and barons have a 

 profile or side-standing helmet of steel ornamented with bars ; the 

 full-faced helmet of steel, with the visor or bevor open, is for baronets 

 and knights ; the profile helmet, steel, with the visor closed, for an 

 esquire. 



HEMATEIX. [HF.MATI*.] 



HKMATIN (C^H^O,., 4-2 aq.), Amatory/in, the colouring-matter of 

 the Ilfematoxjilfni campechianum, or logwood, discovered by Chevreul. 

 It is prepared by evaporating a watery infusion of logwood to dryness, 

 treating the residue with alcohol, filtering the spirituous solution, and 

 evaporating it to the consistence of a syrup. If a certain quantity of 

 water be added to this, and evaporation be performed with a gentle 

 heat, the heraatin crystallines, and requires only to be washed with a 

 little alcohol and dried. Hematin crystallises in small lamime of a 

 reddish colour. The taste of hematin is at first sweet and astringent, 

 and afterwards bitter. It is decomposed by heat. Water dissolves 

 hematin, and the solution is of an orange-red, at 212 Fahr., but 

 becomes yellow on cooling. Acids saturated with oxygen turn its 

 colour first to yellow and afterwards to red; the alkalies in small 

 quantity render hematin purple, and when in excess violet-blue, and 

 eventually decomposing it, make it yellowish-brown. In contact with 

 oxygen and alkalies hematin gives tumatein (C 3 ,H,,0 1 ,), which unites 

 with two equivalents of ammonia, forming a compound of a fine purple 

 colour. 



This colouring principle is a constituent part of all the colours pre- 

 pared with logwood, and the changes which it undergoes by the action 

 of acids and alkalies render it useful as a re-agent to detect their 

 presence. 



HEMATOCRYSTALLIN. A red crystalline albuminous matter 

 found in blood under certain circumstances. It is soluble in acetic 

 acid, but insoluble in potash. Ammonia dissolves it with the pro- 

 duction of a peach-blossom colour. It contains, according to Lehmann, 



Carbon 55-24 



Hydrogen 7-12 



.Nitrogen 17-31 



Sulphur . . . . ..*21 



HF.MATOIDIN (C..H.NO, ?). A bright orange-red crystalline body 

 formed in blood which has effused into the tissue of a living animal. 

 These crystal* are observed from the fourth to the twentieth day after 

 the hemorrhage. They are insoluble in water, alcohol, ether, and 



acetic acid, but dissolve in ammonia with a bright red tint, which soon 

 becomes orange-yellow and finally brown. 



HEMATOSIN (C^H^N^Fe ?), the red colouring-matter of the 

 blood ; it has not however been obtained in a perfectly pure state, 

 owing to the difficulty of separating it from other substances, and to 

 the facility with which it undergoes change : when the coagulum of 

 blood, which has been drained, is put into water, the colouring-matter 

 dissolves and forms a fine crimson-coloured solution; this when 

 exposed to a moderate heat dries and forms a brittle dark red sub- 

 stance, which is again soluble in water. When it has been acted upon 

 by heat and alcohol it coagulates, owing to the albumen which it 

 contains, and it is then insoluble in water, but soluble in potash ; the 

 red solution is rendered black by carbonic or sulphurous acid, but its 

 colour is heightened by air on. account of the oxygen which the latter 

 contains ; nitrous oxide renders it purple, and sulphuretted hydrogen 

 greenish-black. 



A peculiarity of hematosin is its containing iron, which does not 

 occur in other parts of the animal system : when the clot of blood is 

 decomposed by exposure to heat and air, the residue treated with 

 hydrochloric acid exhibits by the usual tests the presence of peroxide 

 of iron, unaccompanied by phosphoric acid. So also when dried blood 

 is moistened with a little concentrated sulphuric acid, on the addition 

 of water a solution is obtained which with ammonia yields a precipitate 

 of peroxide of iron. 



The hematosin of bullocks' blood, but not quite pure, for the 

 reasons already stated, analysed by Mulder, yielded the following 

 ingredients : 



Carbon 66-49 



Azote IO-J4 



Hydrogen 5-SO 



Oxygen 11-01 



Iron 6-66 



100-00 



65-91 

 10-54 



5-37 

 11-75 



6-58 



100-15 



HEMATOXYLIN. [HEMATI.V.] 



HEMERALOPIA, a word which ig now used to signify " night- 

 blindness," though in fact it means "day-seeing," being similarly 

 formed to the genuine Greek word "nyctalopia" (vvKTa\anria) , which 

 means " night-seeing." Much confusion has arisen in regard to the 

 use of the two words, in consequence of an error committed either by 

 Hippocrates or one of his early editors. In the second book of his 

 ' Pnedicta,' he says, " We call those nyctalopes who see by night ; " 

 but in the fourth and sixth books of his ' Epidemics,' the disease which 

 he speaks of under a similar term appears to be that in which the 

 patienta are blind at night; and his translators, Paulus ^Egineta, 

 .Etius, and Galen, quote various authorities to show that those only 

 are properly called uyctalopes who are affected with night-blindness. 

 They have been followed by Bontius, Sir G. Blaue, and many naval 

 surgeons, who apply to the present disease the name of nyctalopia, or 

 dysopia tenebrarum. Limifeus and Vogel however define nyctalopia 

 to be night- vision, and call night-blindness, hemeralopia ; and as their 

 meanings have been since received by Scarpa, Lawrence, and all the 

 chief writers on diseases of the eyes, they will be adopted here. 



Night blindness is a common disease amongst seamen in the East 

 and West Indies, the Mediterranean, and in all hot countries, and 

 affects in a slighter degree soldiers and the natives in the same parts of 

 the globe. To persons affected by it, all objects appear at sunset as if 

 covered with an ash-coloured veil, which becomes gradually denser, 

 and at last involves them in complete darkness. In slight cases they 

 can see by bright candle-light or by moon-light ; but after the disease 

 has lasted a few days, even the largest objects are invisible after sunset, 

 and the patients have to grope their way even where the moon or 

 candles are shining brightly. The disease will daily increase in severity 

 if not judiciously treated, till the sight becomes weak by daylight, and 

 so disordered that total blindness might be apprehended, though it 

 very rarely follows. The pupils are generally dilated, and at night 

 cannot be made to contract even by a brilliant light. 



The most probable cause of this disease is the exhaustion of the 

 retina, produced by the continued glare of a bright sun, either directly 

 transmitted to it, or reflected from the clear waters of the tropical seas, 

 or the bright sands of their shores ; a condition of which one may form 



others with scurvy. 



The disease will generally get well, though it may exist for weeks or 

 months. The most successful treatment is the repeated application of 

 small blisters to the temples. Mr. Bampfield cured by this means 

 upwards of 300 cases. This treatment never failed ; but in some 

 instances its effects were accelerated by the administration of purga- 

 tives and other medicines adapted for the coincident symptoms of 

 scurvy or of disordered digestion. The best description of the disease 

 is in Mr. Barnpfield's ' Essay on Hemeralopia,' in the 5th vol. of the 

 ' Medico-Chirurgical Transactions.' 



Nyctalopia, night-vision, or day-blindness, probably never occurs as 

 a separate disease. It is often a symptom of scrofulous ophthalmia and 

 other diseases where the eye is so irritable that the stimulus of day- 



