206 



KNOWLEDGE. 



[Septembek 1, 1897. 



Prof. Fraser is of opinion that many organic poisons 

 which get introduced into the system are rendered non- 

 effective by the action of the bile. This throws consider- 

 able light on the great service rendered by bile to the 

 system, besides its necessary use in the process of digestion. 

 It was long known that bile has an antiseptic action, 

 diminishing the putrefactive changes of the intestinal 

 contents ; but Prof. Fraser has good reason to believe 

 that it acts as an antivenene for many poisonous 

 substances which get into the stomach with the food, 

 and which cannot be detected in the preparation of the 

 food. 



Thus gradually is Prof. Fraser enlightening the world 

 by his successful experiments on the antidotes to poisons. 

 The addition of snake bile to the immunized serum to 

 form a powerful antivenene is a most valuable discovery, 

 and gives evidence of the great advance made in medicine 

 during recent years, when the thyroid preparation for 

 myscedema and the antitoxin for diphtheria, and such like, 

 have startled the medical world. Prof. Fraser deserves 

 the hearty thanks of the scientific world for his unwearying 

 patience in investigating this most important and com- 

 paratively new subject. 



PIT-VIPERS. 



By Lionel .Jervis. 



THE classification of ophidians is the bane of zoology, 

 and of the making of catalogues there is no end. 

 Nevertheless, we have reason to congratulate our- 

 selves on the classification of the Crotalince in the 

 " Catalogue of Snakes in the British Museum 

 (Natural History)," Vol. IH., dated 1896. Following, 

 apparently, the lines adopted for the classification of the 

 rattlesnakes, the author has, by a happy analogy, brought 

 under the one comprehensive heading of Lachesis, in- 

 cluding forty species only, a group of serpents described 

 in the works of former naturalists by considerably over 

 one hundred and twenty different titles. 



I do not propose here to differentiate minutely between 

 the various species by enumerating those in which the tail 

 is or is not prehensile, or in which the second upper 

 labial forms the anterior border of the loreal pit, or in 

 which the pit is separated from the labials by scales, etc., 

 etc. Students of herpetology are probably already in 

 possession of the catalogue, to which they can readily 

 refer ; while to the casual reader such details would only 

 be tedious. 



I regret that I am unable to say anything new about the 

 most characteristic feature of the Crotalina,, the loreal pit, 

 lying between the eyes and the nose. The nearest approach 

 to the true solution of the question appears to me to bs 

 the theory that it contains the organ of an unknown sense. 

 On this point a famous herpetologist writes that it was 

 found that " the lining was supplied with a thick nerve, 

 ending in a way the only analogue of which is found in the 

 retina of the eye and the labyrinth of the ear " ; and, 

 again : " It does not seem doubtful that we have here to do 

 with a true sense organ." It is not necessary to quote 

 more extensively in respect of a subject on which I am not 

 prepared to elucidate any of the solutions already offered ; 

 but whether the pit supplies a distinct sixth sense, or 

 whether it is supplementary to any of the others, it is 

 certain that few creatures have greater need of help in 

 this direction, for it is evident that the sense of taste is 

 almost altogether absent, while their sight and hearing 

 are notoriously feeble. 



In the popular mind the viper is regarded with feelings 



In which the element of fear is predominant, and perhaps 

 it will not be amiss to discuss how far this fear is justified 

 with regard to the iMchrsis family in comparison with 

 other venomous snakes. In order to arrive at a satis- 

 factory conclusion on this subject it will be necessary to 

 consider three main points — the method of attack, the 

 virulence of the venom, and the disposition of the snake. 

 The two latter vary with the species, and will be touched 

 on later on, and I shall now endeavour to explain the 

 method of attack of a large pit-viper. 



When disturbed or irritated the snake throws itself into 

 coil, the posterior half of the body — the base of operations — 

 being in spiral circles, while the anterior half — the aggres- 

 sive portion —is bent back on itself in several lateral curves ; 

 the head is slightly raised and is directed towards the 

 object to be struck. The moment this comes within range 

 the muscles on the outer sides of the curves are suddenly 

 and violently contracted, so that the head and the upper 

 part of the body are darted forward with great rapidity ; 

 " Le serpent se deroule," as an old French writer expres 

 sively puts it. 



As soon as the forward thrust has commenced, but not 

 till then, the mouth is opened to an angle of nearly one 

 hundred and eighty degrees, the skull itself being bent 

 backwards on the neck to a considerable extent. Simul- 

 taneously the snake, by the action of the spheno-pterygoid 

 muscle, causes the maxillary bone — in all vipers very 

 short — to partially revolve, so that the fangs are elevated 

 from their normal position parallel to the roof of the 

 mouth, to an angle of forty-five degrees (or rather more, 

 so as to allow for the curve of the fangs) to the upper jaw, 

 so that the points may be directed straight towards the 

 object of attack. It has been frequently stated that the 

 elevation of the fangs is due to the opening of the mouth, 

 owing, no doubt, to these actions usually taking place 

 simultaneously ; but, as a matter of fact, this is not the 

 case, as the snake has perfect control over them, erecting 

 and depressing them at will, either together or indepen- 

 dently of each other. 



As soon as the fangs have entered the tiesh of the 

 victim, the muscles which act in antagonism to the 

 spheno-pterygoid depress the points, driving them deeper 

 into the wound ; and, immediately after, the snake closes 

 its lower jaw sharply onto the bitten part, with the 

 double object of momentarily retaining its hold and 

 of injecting the poison, the venom gland being com- 

 pressed by one (amongst others) of the muscles closing 

 the jaw. 



All these actions take place almost co-instantaneously, 

 and particular attention is directed to the two last, as they 

 considerably modify the danger of the attack, for should 

 the snake misjudge its distance — a not infrequent occur- 

 rence — the depression of the fangs may take place a fraction 

 of a second too early, and consequently the outer curves 

 and not the points will strike the skin, and the flesh wUl 

 not be penetrated. Moreover, in order to avoid biting its 

 own lower jaw, the snake separates its fangs (the extremities 

 of the mandibulars being at the same time brought closer 

 together), so that they point outside the mouth, and con- 

 sequently, if the object is narrow — the finger, for instance — 

 it sometimes happens that they will pass on either side of 

 it. Nevertheless, it is perfectly clear that any object in 

 the line of the thrust will be penetrated, except at the 

 commencement of the stroke, before it has gathered force, 

 or at the finish, when thp points of the fangs may have 

 been depressed too soon. 



By way of comparison let us now consider the attack of 

 the cobra (Xaja), as one of the best known and most 

 venomous of serpents. Here it is important to appreciate 



