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XLIV. Observations intended to shoiv that the progressive 

 Motion of Snakes is partly perjormed by means of the 

 Ribs. By Everard Home, Esq, F.R.S.* 



On a former occasion I laid before the Society a descrip- 

 tion of the mechanism oF the hood of the cobra de capello 

 snake of the East Indies, the coluber naja of Linnaeus, in 

 which the ribs of the neck are shown to be formed in a par- 

 ticular manner; so that, when they are raised, the skin be- 

 comes stretched out, and puts on the appearance of a hood. 

 The ribs so employed have several peculiarities, which I 

 took for granted were confined to those of the neck, for I 

 was not in possession of the bodies of the snakes, and there- 

 fore could not examine the others ; but have since found 

 that many of these peculiarities are not only common to all 

 the ribs of this snake, but to those of the whole tribe. 



This fact, as it escaped my observation at that time, 

 would have still done so, had it not been for the following 

 circumstances. 



A coluber of unusual size, lately brought to London to 

 be exhibited, was shown to Sir Joseph Banks; the animal 

 was lively, and moved along the carpel briskly : while it 

 was doing so, Sir Joseph thought he saw the ribs come 

 forward in succession like the feet of a caterpillar. This 

 remark he immediately communicated to me, and gave me 

 an opportunity of seeing the snake and making my own 

 observations. 



The fact was readily established, and I could feel the 

 ribs with my finjiers as they were brought forward : when 

 a hand was laid flat under the snake, the ends «)f the ribs 

 were distinctly felt upon the palm, as the animal passed 

 over it. 



This becomes a more interesting discovery, as it consti-^ 

 tutes a new species of progressive motion, and one widely 

 different from those already known. 



In the draco volans the ribs form the skeleton of the 

 wings, by means of which the animal flies, the five posterior 

 rilis being bent backwards and elongated for that purpose, 

 so that in that instance the procressive motion is performed 

 by the ribs; but those particular ribs are superadded lor this 

 pur|)0se, and make no part of the organs of rLspiraiion ; 

 whereas, in the snake, the ribs arc so conslnictfd as to per- 

 form their office with respect to the lungs as well as pro- 

 gressive motion. 



• From the Phllnsoplilcal Transiictious for 1'J12, part i. 



Vyl.40, No. 174. Ot^ 1812. Q That 



