July 2, 1894.] 



KNOWLEDGE 



161 



But a recent attempt has been made by Mr. H. T. Vivian, 

 F.R.A.S., to carry this discovery still further back, and to 

 attribute it to Dr. Eobert Hooke, the famous first Curator 

 of the lioyal Society, an observation of whose he quotes 

 in the columns of one of your contemporaries, illustrating 

 it with what purports to be an accurate copy of the original 

 engraving in the Philosopliiral Traimactiorif: for 166(). 

 Now this is a point of such curious historical interest that 

 I have taken the pains to inspect the original engraving, 

 which, 1 am boimd to say, I do not find to bear out Mr. 

 Vivian's contention. Through the kindness of my friend 

 Mr. C. Leeson Prince, F.E.A.S., who has taken a photo- 

 graph from the plate in the Philosophical Tranmctions, I 

 am enabled to give an accurate reproduction of it here. 

 Should it be rendered in these columns with the exactness 

 which usually distinguishes your beautiful protographic 

 illustrations, I think that the following facts will become 

 evident to the careful observer : — In the first place, the lines 

 representing shading between ring B and the body of the 

 planet will be seen to be carried uniformly across that 

 interval, and the apparent darkness in actual contiguity with 

 the globe of Saturn to have had its origin in the printing. 

 But, furthermore, if we are to accept this seeming difference 

 of tint within the ansae as an attempted delineation of the 

 actual dark ring, what interpretation are we to put upon 

 the perfectly apparent, carefully engraved, and cross- 

 hatched dark lune outside of the foUowimj ansa .' Did — or 

 did not — Hooke see an exterior dark ring in this portion 

 (and nothing whatever outside of the western ansa) or 

 what ■' Surely no imprejudiced obser\er, approaching the 

 consideration of this question without prepossession, will 

 deny that this strange feature is much more definitely 

 shown than is that which Mr. Vivian imagines to represent 

 ring C. WiLLiAJi Noble. 



To the Editor of Knowledge. 



Sir, — In your note to my letter published in the May 

 number, you ask how I can distinguish between the effects 

 of the different concurrent circumstances which accompany 

 " changes of air." This is only to be done by making use 

 for observation of chance occasions when the usual "con- 

 current circumstances" are absent, and of those occasions 

 when the effects'of similar circumstances without changes 

 of air may be observed. The following is an unusually 

 plain example of what I refer to. Two children of my 

 own went into the country for three weeks in very bright 

 weather ; three others stayed in London, but were made 

 to spend the greater part of the day in a neighbouring 

 open space. The result was that they all got much 

 strengthened and bronzed, and equally so. 



When one is " below par " — that is, when one's full vigour 

 is lessened, the lowering influence may almost always be 

 discovered by careful inquiry. It may be over-exertion 

 and too little sleep, or anxiety, or constant family cares, 

 or spending too much time indoors, or living in an over- 

 heated room or street, or cold or many other things ; but 

 it will be found that in those cases where the change of air 

 is not accompanied by relief from the injurious influence, 

 no good is effected. On the other hand, the benefit that is 

 usually obtained by " a change " may almost always be 

 traced by inquiry to causes much more evident than any 

 difference in the composition of the air. For instance, a 

 woman living in a stufl'y house in an ill-ventilated street is 

 rendered languid and oppressed by hot weather. She goes 

 on to a breezy common, and although the temperature of 

 the air there may be nearly the same, its motion about 

 her is much more rapid and constant, and therefore its 

 cooling effect much greater, and ahe gets correspondingly 



braced. With " change of air," moreover, people are 

 ready to make changes of habits which they cannot, or 

 have not the force of will to make at home. Thus the 

 circumstances concurrent with "change of air" which 

 act beneficially are usually of a negative character, and 

 consist in the leaving behind some lowering influence. 

 This opinion is not in any way opposed to the fact that the 

 air in different places varies much in its condition (without 

 change in composition), and so is more or less beneficial or 

 detrimental in various diseases and states of constitution. 



I am, Sir, yours obediently, 

 Tunbridge Wells, Edw. G. Gilbert, M.D. 



May 29th, 1894. 

 [The isolated instances referred to by Dr. Gilbert can 

 hardly be taken as sufficient to upset the generally received 

 theory as to change of air. But if those who have charge 

 of schools or institutions would make notes of the effects 

 produced by change of habit on the weight and strength 

 of groups of individuals as compared with other 

 groups taking change of air, we should have something 

 more definite to go upon and the facts accumulated 

 might possibly be of great value to the community. — 

 A. G. Ranyari).] 



THE VENOM OF THE VIPERS. 



By C. A. Mitchell, B.A.Oxon. 



POISONOUS serpents are classified in two main 

 groups — the Coluhriim, with poisonous fangs per- 

 manently erected, and the Vipenna, nearly all of 

 which have fangs which they can erect or depress 

 at will. The cobra may be taken as the type of 

 the former, while to the latter belong the Crotalida. or 

 rattlesnakes, and the various species of vipers. The 

 Vijieridm are distinguishable from the Crotalida; in having 

 no pit between the eyes and the nostrils, but in many 

 other respects they closely resemble each other. The 

 chemical and physiological eft'ect of their venom is also 

 very similar, and presents marked differences to that of 

 the cobra, of which a description was given in a previous 

 paper. 



The venom from the common viper {I'elios Bents) when 

 freshly obtained is a yellow, viscid licjuid which dries into 

 a gummy inodorous mass. As early as the beginning of 

 last century it had attracted the notice of scientific men, 

 for in 1702 we find that a book was published by Dr. 

 Richard Mead called ■' The Mechanical Action of Poisons," 

 in which he gave an account of his experiments on the 

 viper poison. Misled by the magnified appearance of a 

 drop of the venom when drying, he came to the conclusion 

 that the poisonous principle was due to the presence of 

 caustic saline salts. "These saline particles," he writes, 

 " were now shot out as it were into crystals of an incredible 

 tenuity and sharpness, with something like knots here and 

 there from which they seemed to proceed ; so that the 

 whole texture did in a manner represent a spider's web, 

 though infinitely finer and more minute." 



This book ran through several editions and Mead's 

 theories were accepted until, in 1767, the Abbe Fontana, 

 naturalist to the Grand Duke of Tuscany, published his 

 classical treatise on viper poison. He proved that no salts 

 were present, as Mead affirmed, and brought forward 

 instead the suggestion that the venom was a natural gum. 

 He also showed that it might be swallowed with impunity 

 by getting his servant to make the experiment on several 

 occasions, the only unpleasant result being a tingling 

 sensation on the tongue, which lasted five or sis hours. 

 In 1843, Prince Lucien Bonaparte obtained an active 



