230 



GLANCE 



GLANDS 



and many ruined memorials of the middle ages. 

 Of these last Oystermouth Castle, Caerphilly 

 Castle, and Castle Coch are the finest specimens. 

 Cardiff Castle is a tine restored edifice. See Thomas 

 Nicholas, History of Glamorganshire (1874). 



Glance ( Ger. Glanz ), a term often applied in 

 popular language, and also by mineralogists, to a 

 numerous order or family of minerals, of which 

 Galena ( q. v. ) or Lead-glance may be regarded as a 

 type. All of them are metallic, and many of them 

 are known by names indicating the metal which is 

 their principal constituent, as Lead-glance, Silver- 

 glance, Bismuth- glance, &c. In these and many 

 other species the metal is combined with sulphur, 

 so that the mineral is a sulphuret ; but there are 

 also numerous species of glance in which sulphur 

 is not present, but selenium, arsenic, or tellurium 

 takes its place. In some kinds, also, two or more 

 metals are present instead of one, in combination 

 with one or other of these non -metallic or semi- 

 metallic substances. Thus, Gold-glance, or Silvan- 

 ite, consists of gold and silver in combination with 

 tellurium ; it occurs in veins in porphyry, in Tran- 

 sylvania, and is wrought for the sake of both the 

 precious metals whicn it contains. Several kinds 

 of glance are very valuable ores, as Lead-glance 

 or Galena, Copper-glance or Redruthite, and Silver- 

 glance or Argentite. Although some mineralogists 

 have adopted the names Pyrites, Glance, and Blende 

 as names of orders or families, the limits and dis- 

 tinctions of these groups are not well marked. All 

 kinds of glance are fused without much difficulty 

 by the blowpipe. They are also soluble in acids. 



Glance-coal. See ANTHRACITE, and COAL. 



Glanders or EQUINIA, a malignant, conta- 

 gious, and fatal disease of the horse and ass, due to 

 the introduction into the body, or perhaps to devel- 

 opment within it, of a virulent organism called 

 the Bacillus mallei. Discovered by Dr Struck 

 of Berlin, and almost identical with the microbe 

 of tuberculosis, this organism is about TnrJfisth of 

 an inch broad, but varies from ^nnjth to T^^th 

 of an incli in length. This microbe, whilst 

 infecting the whole system, shows specific effects 

 more especially upon the mucous membrane of the 

 nose, upon the lungs, and on the lymphatic system. 

 Glanders and its modification Farcy are capable of 

 transmission to man on whom the virus increases 

 in malignancy to sheep, goats, dogs, the feline 

 species, and even to mice and rabbits ; pigs and 

 fowls resist the contagion, and until lately cattle 

 were thought to do so, but experiments have 

 thrown doubt upon this. 



In a typical case of glanders ulcers form in the 

 nose, characterised by ragged and inflamed edges, 

 discharging a viscid or sticky pus ; a hard tumour 

 forms under the jaw; the animal usually loses 

 condition very rapidly; farcy buds and ulcers 

 appear on the skin in various regions of the 

 body ; the limbs swell ; and the animal dies a 

 loathsome object. Any cause which interferes with 

 the purity or integrity of the horse's blood or pro- 

 duces a deteriorated or depraved state of his system 

 predisposes to glanders. It has been frequently 

 developed in healthy animals by their breathing 

 for a short time a close, impure atmosphere, and 

 cases of this sort were thus produced amongst the 

 horses of several cavalry regiments during their 

 transport in badly - constructed, overcrowded 

 vessels to the Crimea in 1854. Confined, over- 

 crowded, badly - ventilated stables are almost 

 equally injurious, for they prevent the perfect 

 aeration of the blood, and the prompt removal of 

 its organic impurities. Bad feeding, hard work, 

 and such reducing diseases as diabetes and in- 

 fluenza also rank amongst the causes of glanders. 

 Government by the Act Viet. 16 and 17, of date 



14th August 1853, very properly compels the 

 immediate destruction of every glandered horse. 

 Glanders, like farcy, is dealt with by the Con- 

 tagious Diseases Acts, 1878-86. Horses frequently 

 have the disease in a chronic form, and if well 

 fed and managed they might sometimes live and 

 work for years in this condition : in the old coach- 

 ing-days some stages were known to be worked 

 by glandered teams. But no animal with glander- 

 ous ulcers or discharge should on any account 

 be preserved ; for, besides being perfectly incur- 

 able, the fatal disease is communicable not only 

 to healthy horses, but also to human beings. 

 The symptoms of glanders in man are very similar 

 to those in horses, the disease in man being gener- 

 ally regarded as fatal. The only available treat- 

 ment consists in good nutrition, tonics, disinfect- 

 ants, and detergent applications. In 1889 one of 

 two Viennese surgeons who had been experiment- 

 ing with bacilli from a human case of glanders, and 

 artificial cultures from these bacilli, was infected 

 with this disease in its most malignant form, and 

 died. 



Glands are secreting structures, the component 

 elements of which in various ways alter the 

 material brought to them by the blood, extracting 

 and excreting waste products as in the kidneys, or 

 manufacturing valuable by-products, such as the 

 glycogen and bile of the liver. In a typical gland 

 three parts have to be distinguished : (a) the 

 secreting cells usually enclosed in some more or 

 less distinct membrane; (b) the surrounding net- 

 work of blood-vessels ; and (c) the duct by which 

 the products of secretion pass from the gland. 



Most true glands are pockets of glandular skin, 

 mucous membrane, or epithelium, and occur on the 

 outer surface of the body, as in the sweat-glands 

 of the skin ; on the lining of the alimentary canal 

 e.g. salivary glands, liver, pancreas, intestinal 

 glands, &c. ; or on other internal surfaces e.g. in 

 connection with the genital ducts. They may be 

 classified according to their origin from ( 1 ) the 

 ectoderm or epiblast, (2) the mesoderm or meso- 

 blast, and (3) the endoderm or hypoblast. Thus, 

 ( 1 ) in connection with the outer skin there 

 are, besides glandular cells (so-called unicellular 

 glands), numerous secretory pockets, such as the 

 sweat, scent, anal, poison, adhesive, byssus, slime, 

 spinning, and mammary glands. At each end of 

 the ( endodermic ) gut there is a more or less pro- 

 longed invagination of ectoderm, and the glands 

 connected therewith are obviously in the above 

 embryological category. (2) The kidneys of most 

 animals illustrate glands of mesodermic origin, but 



a b 



f 



Diagram of Glands (from Hertwig) : 



a, simple tubular gland ; 6, branched tubular glands ; c, simple 

 acinous glands ; d, branched acinous gland ; e, duct of gland ; 

 /, sac of gland. 



it is inaccurate to speak of the reproductive organs 

 (as is often done) as glands. They liberate 

 reproductive cells, differentiated elements, not 

 products of secretion. (3) The numerous glands 



