OPHIDIA. 



OPHIDIA. 



" The external layer of cement is Tery thin where it covers the 

 crown of the tooth ; it is best seen at the line of union of the co- 

 adapted margins of the inflected tooth. At this part the cement is 

 more abundant in the viper's tooth, and its transparency permits a 

 bristle inserted into the poison-canal to be seen through it. The 

 layer which coats the inflected surface of the fang is thinner than the 

 outer one, which, from its transparency, has been regarded as enamel. 

 There is however no trace of true enamel upon the teeth of the 

 poisonous serpents, any more than upon those of the innocuous 

 species. The cells of the cement are more minute and inconspicuous 

 in the poison-fang than in the simple teeth of the Python and Boa. 



"The teeth of all Ophidians are developed and completed in the 

 original seat of the tooth-germs in all animals, namely, the mucous 

 membrane or guta covering the alveolar border of the dentigerous 

 bones. This gum presents the same lax tissue and is as abundantly 

 developed as in the Pike, Lophius, and many other fishes, in which it 

 likewise serves as the nidus and locality for the complete development 

 of the teeth. 



" The primitive dental papilla in the common harmless snake very 

 soon sinks into the substance of the gum and becomes inclosed by a 

 capsule. As soon as the deposition of the calcareous salts commences 

 in the apex of tlie papilla, the capsule covering that part becomes 

 ossified and adherent to the dentine, and the tooth begins to pierce 

 and emerge from the gum, before its mould, the pulp, is half com- 

 pleted. Fresh layers of cells are successively added to the base of 

 the pulp, and converted by their confluence and calcification into the 

 tubular dentine, until the full size of the tooth is attained, when its 

 situation in the pum is gradually changed, and its base becomes 

 anehylosed to the shallow cavity of the alveolar surface of the bone. 



'' In the posterior part of the large mucous sheath of the poison- 

 fang, the successors of this tooth are always to be found in different 

 stages of development ; the pulp is at first a simple papilla, and when 

 it has sunk into the gum the succeeding portion presents a depression 

 along its inferior surface, as it lies horizontally, with the npex directed 

 backwards; the capsule adheres to this inflected surface of the pulp. 

 But how the cylindrical cavity of the dilated fold is occupied in the 

 loose growing poison-fang, and by what contrivance it is brought into 

 the same relation with the severed duct of the poison-gland as the 

 displaced fang which it succeeds, is not yet clearly understood." 



From the consideration of the teeth we proceed to that of the other 

 organs of nutrition. The os hyoides in the Ophidians bears a strong 

 resemblance to that of some species of Saurians [IGCAJJA; DRACO- 

 NINA]; but the anterior part ig double, and the two long osseous 

 filaments which form it terminate in pointed cartilages, which intro- 

 duce themselves, parallel, into the fleshy tissue of the tongue, and 

 are separated by the hypoglossal muscle. The modifications of the 

 muscles of the jaws are varied, and admirably adapted to the purpose 

 assigned to them. Some are appointed to work the venom-fangs by 

 carrying forward the external pterygoid and superior maxillary bones ; 

 others again are employed in the separation, approximation, and 

 adjustment of the mandibular bones and the whole of the maxillary 

 articulation ; nor are those which act upon the tongue and os hyoideg 

 less complicated ; whilst the peculiar muscles which come from the 

 vertebrae and ribs all assist in the process of deglutition. The mobi- 

 lity of the tongue of the serpents must have struck every observer, 

 and they have been se<n to lap water with it. Serpents cannot be 

 said to have any true pharynx ; for the nostrils, as well as the glottis, 

 open in the mouth, and the oesophagus commences immediately after 

 the termination of the jaws ; and is capable of great extension, BO as 

 to be capable of receiving prey of a very large diameter entire. The 

 stomach is a continuation of the oesophagus, and the intestines are 

 very short, and with but little flexure. The vent or cloaca opens by a 

 transverse slit towards the end of the abdomen, above the origin of 

 the tail, which is often very long. The liver consists of only one lobe 

 of an elongated form, placed on the right, or in the mesial region, in 

 front of the long oesophagus, and accompanies the stomach, furnishing 

 distinct hepatic and cystic canals. The bile is greenish or brown, and 

 the cystic canal comes direct from the liver. The spleen is not large, 

 and is situated on the right near the insertion of the ductus chole- 

 dochus. The pancreas ig situated immediately under the junction 

 of the intestine with the stomachal sac beneath the peritoneum. 



The absorbent powers of the intestines of serpents are great. Messrs. 

 Dumi^ril and Bibron advert to the state of their dejections as a proof 

 of this. They offer, to use their expression, the dry extract of the 

 animal entire, of which only the parts that could not be liquefied 

 remain unaltered, and absolutely in the same situation that they 

 occupied in the carcass of the animal before it had passed through 

 the whole length of the digestive tube. If, for instance, a rat has 

 undergone this process, one may recognise in the dry and shapeless 

 maw the place occupied by the muzzle of the animal, the long whiskers 

 of its cheeks, the down which covered the delicate cartilages of its 

 ears, th hairs of various lengths and colours which correspond with 

 of the back, the belly, and, above all, the tail ; and, finally, even 

 the claws, which remain in their pristine state of integrity. All that 

 was flesh or soft matter in the body has been- completely absorbed ; 

 irthy salt, nevertheless, which gave, by means of its union with 

 the gelatin, consixtence to the bones, still indicates by its presence, 

 specially by its colour, the place they occupied. Dissolution, 



HiT. HIST. DIV. YOU IV. 



compression, and absorption have done their work upon this desiccated 

 mass, which still however contains the elements of nourishment for 

 the larva) of the insects of the family Dermestidce. 



In the faces of the Python which a few years ago devoured its 

 companion in the Gardens of the Zoological Society of London, there 

 were entire scales of the digested serpent. 



There are several interesting preparations of the anatomy of these 

 organs in the Museum of the Hoyal College of Surgeons. 



There is no great difference between the heart of serpents and that 

 of Saurian-'. In the Museum of the Royal College of Surgeons (No. 

 917 B), the heart of a Python Tigris is prepared to show the internal 

 structure as well as the outward form. Professor Owen, who made 

 this preparation, observes that the blood of the general system is col- 

 lected into a large elongated sinus, formed by the union of the inferior 

 with the right superior cava. The left superior cava winds round the 

 back of the left auricle, receives the coronary veins, and terminates in 

 the lower part of the orifice, which leads from the above sinus to the 

 right auricle. This orifice is protected by two semilunar valves. The 

 whole of the inner surface of the auricle, with the exception of theso 

 valves and the opposite valve of the foramen ovale, is reticulated with 

 delicate muscular fasciculi The left auricle receives the blood from 

 a single pulmonary vein, and has a similar reticulated muscular struc- 

 ture : there is no valve at the termination of the vein in this auricle. 

 The blood enters the posterior or aortic division of the ventricle by 

 two crescentic apertures, which are each provided with a single semi- 

 lunar valve, extended from each side of the septum of the auricular 

 orifices. The irregular form and small size of the aortic chamber is 

 displayed by the removal of the posterior parietes of the ventricle. 

 On the opposite side the pulmonary chamber is exposed ; and the Pro- 

 fessor remarks in continuation, that it is of a larger size, of a more 

 regular oval form, and with a smoother surface. The fleshy septum, 

 extending from the base of the ventricle to the space between the 

 roots of the pulmonary and systemic arteries, is incomplete at its 

 upper and anterior part, and there leaves a communication between 

 the pulmonary and aortic chambers : these also, he remarks, inter- 

 communicate by several round apertures of different sizes near the 

 apex of the ventricle, which serve to thoroughly blend together the 

 two kinds of blood before they are expelled thus mixed along the 

 three arteries which separately arise from the ventricles. In this 

 preparation the origins of the pulmonary artery and left aorta only are 

 shown, and they are each provided with a pair of semilunar valves. 

 The carotid arteries are given off from the right aorta, which after- 

 wards unites with the left aorta at some distance below the heart. 

 The gland analogous to the thymus gland is also preserved : its 

 structure is cellular. White bristles are passed through the systemic 

 veins, sinus, and auricle ; and a black one through the pulmouic vein 

 and auricle. The two branches of the pulmonary artery which go to 

 the two separated lungs are distinguished by black bristles, which 

 also indicate the situations of the two ductus arteriosi. (' Catalogue,' 

 voL ii.) 



The mode of respiration in the serpents is thus effected : the glottis, 

 which hag two lips, and represents a very simple larynx, opens in the 

 mouth behind the sheath of the tongue ; by means of the muscles of the 

 os hyoides, which push it, it is raised so as to be presented in a dilated 

 state behind the back nostrils. The vacuum caused by the action of 

 the ribs in the belly tends to dilate the lung, which, through t'je 

 medium of the trachea, immediately admits the air which is introduced 

 during an inspiration : this is slow, continuing for some seconds. This 

 air, when it has performed its office, and has been deprived of its 

 oxygen, U expelled in the same manner, but by an inverse mechanism, 

 which is entirely due to the action of the muscles which tend to 

 approximate the ribs to each other. When it is expelled rather 

 briskly, a sort of vibration or hissing is heard. The respiration being 

 voluntarily accelerated or retarded, the chemical and vital actions 

 which result from it must be naturally excited or abated by that 

 cause. (Dum. and Bibr.) 



As connected with the faculty of respiration, it will be expected that 

 something should be said relative to the voice of serpents, whose 

 hissing has become proverbial. Messrs. Dum<!ril and Bibron state 

 that they hardly think that these reptiles can, as has been said of some 

 colubers, produce hissings (sifflemens) or piercing sounds (sons bien 

 aigus) ; for although their lungs have great capacity, and can furnish 

 air for a long time, Messrs. Dumdril and Bibrou state that they could 

 never hear more than a sort of blowing (soufflement) such as would 

 result from the rapid issue of a current of air through a simple pipe 

 that of a quill for instance. White, however, who was a very good 

 observer, in speaking of the faculty which snakes have of ' stinking se 

 defendendo,' remarks, in his ' Selborne,' that he knew a gentleman 

 who kept a tame snake, which was in its person as sweet as any 

 animal, while in good humour and uualarmed ; but as soon as a stranger 

 or a dog or cat came in, it fell to hissing, and filled the room with 

 such nauseous effluvia as rendered it hardly supportable. These 

 offensive emanations came, no doubt, from the fetid anal glands, which 

 seem, as White observes, to be given to certain serpents as a defence. 

 We, at one time, narrowly watched the habits of serpents, pythons in 

 particular, and have seen them excited in various ways ; but we never 

 remember to have heard them hiss, in the popular acceptation of 

 the term. 



