464 SNAKES OF CEYLON. 



The so-called " hood " is formed by the action of muscles 

 operating upon the ribs in the region behind the neck. 1 have 

 examined a skeleton in the Museum of the Royal College of 

 Surgeons, London, which is well set up in the erect position, 

 and with the ribs fixed as they would be in the expanded hood 

 in life. The atlas (1st vertebra), axis (2nd vertebra), and the 

 3rd vertebra have no ribs, but the 3rd has an elongate rib- 

 like transverse process. The succeeding 27 vertebrae have 

 ribs attached to them that are involved in the production of 

 the hood. These ribs are much less bowed than those in the 

 rest of the body, and enjoy a range of movement greatly in 

 excess of the other corporeal ribs. The 9th is the longest on 

 the left side, and measures 41 mm., and the 10th measuring 

 42 mm. is the longest on the right side. The preceding and 

 succeeding ribs progressively diminish, so that an oval outline 

 is given to the hood. The ribs are set obliquely, forming an 

 angle of 40° to 45° with the long axis of the spine. In the 

 prone state they are directed backwards, outwards, and 

 downwards, and give a contour to the body almost like that 

 in other parts. In the erect pose the corresponding direction 

 of the ribs would be downwards, outwards, and forwards, but 

 any forward tendency is entirely obliterated by the action of 

 a set of dorsal muscles that not only draw the ribs back till 

 they are completely transverse, but also fully straightens 

 them. During full expansion, judging from a freshly dissected 

 hood, I think the ribs are also slightly elevated, and the angle 

 made with the spine thereby rather increased. As the over- 

 lying skin is but loosely attached, it does not in any way 

 hamper the movements of the ribs within, which by their 

 backward extension and elevation enormously stretch it in a 

 lateral direction, at the expense of the ventro-vertebral 

 diameter. The oval shape of the hood and the flattening 

 produced has been well compared to a shallow spoon or 

 skimmer. The hood originates high up in the nape, and the 

 head bent strongly at the atlas joint is carried at right angles 

 to it when spread. The arching of the forebody, and general 

 pose and movement of the cobra j when erect, remind one very 

 forcibly of the carriage of a swan's neck. The dorsal skin 

 is very much stretched when the hood is expanded, so that 



