59T 



VEGETABLE ROUGE. 



VELOCITY. 



VEGETABLE ROUGE. [CAHTHAMIN.] 



VEGETABLE SCARLET. [CARMINE.] 



VEGETABLE SILK. [SILK MANUFACTURE.] 



VEGETABLE WAX. [WAX.] 



VEGETO-SULPHURIC ACID. [SUGAR.] 



VEINS, DISEASES OF. The physiology of the veins may be 

 found in the article CIRCULATION, in NAT. HIST. Div. : in the present 

 article their principal diseases will be described. Of these the most 

 frequent is that in which they become what ia called Varicose , that is, 

 dilated, and unnaturally tortuous, a disease which occurs especially in 

 the subcutaneous veins of the lower extremity. It is the result of the 

 coats of the veins losing their elasticity, and thereby their power of 

 resisting the pressure of the column of blood above them. The loss of 

 elasticity is commonly due to disease of their coats, and is frequently 

 accompanied by an increase of their thickness, and by destruction or 

 impairment of their valves. The dilated veins appear like large 

 tortuous blue canals beneath the skin, or in extreme cases, where 

 many are coiled together, they fortu projecting tumours. They pro- 

 duce inconvenience, both by the pain which results from their dis- 

 tension, and occasionally by the skin over them ulcerating, and allowing 

 them to burst and bleed profusely ; but their more common effect is, 

 that in parts of the skin below them, either spontaneously or after 

 alight injuries, ulcers form, which, in consequence of the circulation 

 being impeded through the dilated veins, are very tedious in healing. 



For this varicose state of the large veins numerous remedies have 

 been proposed ; but the best are only palliative. A temporary remedy 

 is afforded by the recumbent posture, in which the walls of the veins 

 are relieved from the weight of the column of blood : constant advan- 

 tage is afforded by the wearing of a well-applied bandage, or of an 

 elastic stocking, by which a sufficient pressure is applied to prevent the 

 further distension of the veins. The obliteration of the venous trunks 

 may be effected by cutting or tying them in various ways, or by apply- 

 ing some caustic, so as to make the tissues over them slough ; but 

 these proceedings are not without danger, and at present it is very 

 doubtful whether they are often productive of permanent advantage. 

 Patients had better, in general, be content with the palliative remedy 

 of the bandage or elastic stocking. 



A form of varicose disease of the veins, which often accompanies 

 that of the venous trunks, but sometimes exists alone, and with which 

 ulcers of peculiar obstinacy occur, affects the small vessels about the 

 ankle and lower part of the leg. The skin in this disease is almost 

 uniformly red, through the number of small veins that are distended ; 

 the neighbourhood of the ulcer, when one exists, is livid, tense, and 

 shining ; and the ulcer itself is indolent, and very painful, and dis- 

 charges a thin sanies. This state can be treated only by the same 

 remedies as the preceding : but, though commonly overlooked, it 

 is by far the more mischievous disease of the two. 



Varicose affection of the veins of the spermatic cord constitutes the 

 disease named Varicoeele ; and that of the veins of the rectum, or skin 

 around it, forms hemorrhoids, or piles. In these, and in all the other 

 cases, the blood is apt to stagnate in the dilated veins, and to co- 

 agulate within them. The clots thus formed may assume a definite 

 form, becoming elliptical, or more often elliptical with pointed ex- 

 tremities, and the flbrine in them arranges itself in concentric layers : 

 after this they harden, and one of their extremities becoming con- 

 nected with the walls of the vessel, small blood-vessels may form in 

 them, and communicate with those of the surrounding parts. Lastly, 

 the colouring-matter of the blood is removed, and earthy-matter is 

 deposited in the clots, arranged in concentric layers, and giving them 

 considerable hardness : thus pklebo-litku, or vein-stones are formed. 

 They are usually spherical, measuring from one to four lines in dia- 

 meter, lying loose within the veins, and producing no apparent 

 inconvenience, except by obstructing the passage of blood. They are 

 especially common in the dilated veins in the pelvis of old persons, 

 and in the veins of legs which have been long varicose : they neither 

 need nor admit of surgical treatment. 



That which is particularly termed a Varix is either a mass of dilated 

 and tortuous veins, or a single saccular and circumscribed dilatation of 

 a vein, analogous to the circumscribed aneurism of an artery. This 

 circumscribed dilatation is a very rare disease, but in its consequences 

 does not differ from ordinary dilatation. An aneurismal varix is pro- 

 duced when, a communication being made, either by a wound or by 

 ulceration, between an artery and a vein, the latter is dilated by the 

 force of the arterial blood into a circumscribed sac. [ANEURISM.] 



The most serious disease to which the veins are subject is acute 

 inflammation, or pklebitii. It sometimes occurs after the slight wound 

 made in ordinary bleeding ; it is more common after operations upon 

 varicose veins ; and yet more frequently occurs after amputations, of 

 the limbs. Blight cases of phlebitis not unfrequently come on, as if 

 spontaneously, or after exposure to cold, in varicose veins. The dilated 

 veins become hard, like knotted cords beneath the skin, and very 

 painful ; the skin around them inflames, and the parts below become 

 ocdematous; and sometimes a slight erysipelas spreads over the limb. 

 Such affections are usually of little moment ; leeches, rest, and external 

 cold are sufficient to subdue the inflammation, and it often has the 

 favourable result of obliterating the veins, and thus curing the disease 

 by which they were previously affected. 



The more severe phlebitis is a moot dangerous disoaoe. Lymph is 



effused into the cavity of the "vein, and into the tissue of its walls, 

 rendering them thick and hard ; the vein and the tissues immediately 

 around it become exquisitely tender, and the parts whose blood 

 should be returned through the diseased vein are usually 

 oadematous. In a further stage pus is effused into the cavity of the 

 vein, and, mixing with the blood, it may pass into the general current 

 of the circulation, though more commonly the vein is obliterated above 

 the chiefly inflamed part by lymph deposited on its walls, and thus 

 the passage of pus into the circulation is prevented. With the local 

 inflammation of phlebitis a state of low typhoid fever, with muttering 

 delirium and great exhaustion, is usually combined ; and under these 

 the patient dies. 



In connection with suppurative phlebitis a condition often occurs 

 to which the name of purulent diathesis has been given. Its chief 

 characteristic is, that collections of matter form coincidently in many 

 different parts of the body, most frequently in the joints, lungs, and 

 liver, accompanied by a kind of fever similar to that which attends 

 phlebitis. It has been thought that this state depends on pus formed 

 in an inflamed vein being carried into the circulation, and deposited 

 again in some remote part ; or that there is a kind of metastasis of 

 suppuration from the vein to the parts secondarily affected. But cases 

 occasionally happen in which all the signs of the purulent diathesis are 

 well marked, although no vein is diseased ; so that there is no necessary 

 connection between the disease and phlebitis, although in the tendency 

 to suppuration the veins generally take a prominent place The most 

 probable explanation of the disease is, that some morbid matter, such 

 as is formed in the decomposition of the discharge from sores or wounds, 

 is introduced into the blood, whose chemical composition it impairs, 

 engendering a state in which pus is apt to be formed, and in which, as 

 in typhoid fever, every function is seriously disordered. 



The treatment of these cases of acute phlebitis and purulent diathesis 

 cannot be laid down in general terms. Very commonly the former 

 requires the coincident employment of large local bleedings, and of 

 medicines and regimen calculated to maintain the patient's strength. 

 The due observance of the indications for one or both of these pro- 

 ceedings affords the only prospect of success ; but most frequently the 

 best directed means are ineffectual. 



One of the most fatal forms of phlebitis ia that which affects the 

 veins of the uterus and the neighbouring parts after labour, and which 

 chiefly constitutes one of the diseases included under the name of 

 puerperal fever. Pklegmaria dolens, or phlegmasia alba,, is due to 

 phlebitis of a less severe kind affecting the iliac or femoral vein, or 

 both, and many others adjacent to them. By obliterating the venous 

 trunks, and preventing the circulation through them, the disease gives 

 rise to the firm oedema, accompanied by the tightness and glossy 

 paleness of the skin of the leg and thigh, which peculiarly indicate it. 

 It occurs sometimes, but rarely, after exposure to cold : its usual origin 

 is in a comparatively slight inflammation of the veins of the pelvis of 

 women duriug pregnancy, or after delivery, which extends from them 

 to the veins of the lower extremity. It is attended by the same tender- 

 ness and hardness of the diseased veins as exist in other cases of 

 phlebitis ; and in its treatment, as in theirs, the general state of the 

 patient's health, and the degree and extent of the local aSection, 

 considered together, must determine the measures to be adopted. 



VELLUM. [PARCHMENT.] 



VELOCITIES, VIRTUAL. [VIRTUAL VELOCITIES.] 



VELOCITY. This word, rendered into English, is simply swiftness 

 or quickness, and would be soon disposed of, if it were not that various 

 circumstances connected with its measure and calculation render its 

 consideration one of the most useful exercises which the student can 

 have, not only in mechanics, but also in pure mathematics. And since 

 the views which must be developed in treating properly of this word 

 are almost identical with those which arise in explaining the meanings 

 of other words nearly as important, we have made references from all 

 quarters to this article, which, though they will increase its length, 

 will upon the whole save room. 



The difficulty in the way of a beginner, which he meets with in 

 acquiring a clear notion of the measure of velocity, is the tendency to 

 confound the velocity and its measure ; a tendency which is increased 

 by any elementary work which hastens too rapidly to the mathematical 

 treatment of the word. The consequence of this confusion is (since 

 the measure of velocity must be a length described, or rather a length 

 capable of being described) a want of power to distinguish between the 

 space which a body dues describe in a given time, and that which, 

 judging from its velocity, it seems to be going to describe at the 

 beginning of that time. Hence arise many notions mathematically 

 false : these might perhaps be prevented by attributing volition to the 

 moving particle, and distinguishing between its apparent intention at 

 the beginning of the given time and that which it actually accomplishes 

 in the given time. Such an illustration would probably receive no 

 approbation ; but the errors to which it would lead would not be of 

 the least consequence in mathematics. 



A point ia in motion, and during a certain second it moves over ten 

 feet : if the same thing should hnppen in preceding and succeeding 

 seconds, there is a presumption that the body is moving uniformly at 

 the rate of ten feet a second ; that is to say, there is a presumption 

 thnt, in any portion of time whatsjever, during its motion, there is a 

 length described which bears tu ten feet the same proportion as that 



