92 



KNOWLEDGE 



[April 1, 1898. 



victims could be rendered less violent. They seem to have 

 been disinclined to exercise or develop their muscular power 

 to crush or smother them like the constrictors ; the only 

 alternative was to paralyze them. Nature accordingly set 

 to work to modify a portion of the salivary gland, and to 

 impregnate the saliva wiih venom, or to develop the 

 poisonous properties already existent therein. Here, then, 

 the serpent had a store of the composition necessary for 

 its purpose ready to hand. At the same time a groove 

 began to be formed in two or three of the teeth at the back 

 of the upper jawbone (that is to say, those below the 

 salivary gland), and gradually became deeper, thereby 



of the mouth until it could find shelter in the reserve 

 fang which is advanced to take the place of the broken 

 or discarded one ; in either of these contingencies it 

 would in all probability be irretrievably damaged. In 

 reality the duct terminates in the centre of the gum, 

 just between the fangs. It frequently happens that a 

 portion of the venom goes astray between the opening of 

 the duct and the base of the fangs, although they are very 

 close together, and the fleshy sheath that covers the 

 fangs when at rest, but is raised and crinkled up across 

 the gum when the serpent strikes, is said to be instru- 

 mental in preventing the poison being ejected right in 



Fig. 1. — Maxillary bone of innocuous colubrine, shovring solid teeth. FlG. 2. — Maxillary of opliistoglyph, showing development 

 of back fangs. Fio. 3. — Maxillary of innocuous colubrine, showing solid teeth. FtO. 4. — Maxillary of elapine snake, showing solid teeth 

 remaining behind poison-fangs . Fio. 5.— Maxillary of cohra CNaja J, dho-mng almost total absence of solid teeth. Fio. 6. — Maxillary 

 of mamba (VendraspisJ, solid teeth altogether discarded. 



forming a channel by which the poison might be transmitted 

 into the system of the victim. The snake thus became 

 furnished with its poison and the means of injecting it. 

 As a last measure— to make quite sure that the animal, 

 when seized, should not escape — the poison-fangs became 

 somewhat longer than the original solid teeth, and the 

 whole machinery of death was complete (sec Figs. 1 and 2). 

 The prey is entangled in the front teeth and forced back 

 under the fangs. These are then driven home and the 

 venom is injected ; the struggles of the victim almost at 

 once become feeble and soon cease, when it is devoured at 

 leisure. 



This apparatus, though efifectual, is rather clumsy, and 

 we find a great improvement in the proteroglyphs. It is 

 obviously better to have the fangs in the front of the mouth 

 than at the back, as the serpent can then seize its prey 

 and inject the poison at one and the same time, instead of 

 having to work it under the back fangs before it could 

 commence to paralyze it. Before I go any further I should 

 like to have it quite clearly understood that the development 

 of the fangs of the vipers, which are descended fi-om the 

 ophistoglyphs (as I shall endeavour to show later on), is 

 in no way connected with the development of the fangs of 

 the other proteroglyphs, viz. : the elapines and the sea- 

 snakes. In fact, two distinct families of serpents appear to 

 have become venomous at about the same time, quite 

 independently of each other. 



Accordingly, in the elapines and sea-snakes" two of the 

 front teeth on either side of the upper jaw became grooved 

 and enlarged, and a channel was gradually formed from 

 the gland behind the eye to the base of the fangs. The 

 distance, however, between the gland and the poison-fang is 

 never great, and the modification of their relative positions 

 is more apparent than real. As a matter of fact the fangs 

 are always either nearly under the eye or close in front of it. 



For many years it was believed that the duct from the 

 gland to the poison-fang was continued into the fang itself, 

 but research has shown that this view is entirely incorrect. 

 The functional fang is frequently either broken off or 

 shed, in which case the end of the duct would either be 

 carried away or left to dangle unprotected in the front 



Fig. 

 (much enlarged) 



* One species of sea-snake (Distira semperi) is confined to a fresh- 

 water lake in Luzon. 



front, and in directing it down the channel and into the 

 wound. To prevent the venom escaping when the snake 

 is using its jaws without the intent of poisoning, a strong 

 binding muscle is placed close up to the front of the duct. 

 The groove is much deepened and the edges 

 have come closer together, forming a more 

 perfect channel for the passage of the poison ; 

 in fact, in the genus Klaim (the coral snakes) 

 the fang has come to have the appearance 

 of being perforated. The poison - gland 

 itself is much enlarged — in one case 

 (Doliophis) eccentrically so, for it is ex- 

 tended about a third of the way down 

 the body, thereby further upsetting the 

 already disordered internal arrangements of 

 the serpent — and round it is twisted the 

 anterior temporal muscle, so that it can 

 be violently compressed and the poison 

 squirted deep into the wound. It can be 

 readUy seen that this machinery, even in 

 its undeveloped stages, is a great improve- 

 ment on the back-fanged arrangement. . , - , 



T ,1 1- r i-a of elapine snake, 



In the earlier forms numerous solid growing groove, 

 teeth continued to exist behind the poison- 

 fangs, as can be well seen in the sea- 

 snakes, and in the less specialized elapines ( Figs. 3 

 and 4) — examples, Glyphndon and Pseuddnps from New 

 Guinea and the neighbouring coimtries. The serpents, 

 however, with their new and formidable dental armature, 

 began to discover that the envenomed wound caused by 

 their bite paralyzed their prey so quickly that it became 

 less and less necessary for them to retain their hold in 

 proportion as the poison apparatus became more and more 

 developed, and consequently the solid teeth on the maxil- 

 lary bone became useless and gradually disappeared ; so 

 that in the cobra [Xirja), in which the fangs are highly 

 specialized, we only find two or three left (Fig, 5), while 

 in the Eing Hals snake {Scpcdon), the coral snake 

 (Elaps), a,nd in the mamba {l\'7idiaspis) (Fig. 6), they are 

 altogether wanting. 



In some cases the fangs have grown so large that it has 

 become imperative to provide for a certain amount of 

 motion in the maxillary bone, so as to allow them to point 

 slightly backwards when the month is shut, and to avoid 



