VOL. XIII.] PHILOSOPHICAL TRANSACTIONS? 563 



vertebra, which enters a socket of the upper part of the lower vertebra ; as tlie 

 round head of the thigh-bone does the acetabulum of the os ischii, by which 

 means it can turn itself any way. 



Having placed it on its back, we opened it ; and observed that the tendons of 

 the abdominal muscles made a linea alba in the midst of the scales of the belly ; 

 where likewise ran a large blood vessel (fig. 2, rr) arising from the vena cava 

 towards the lower part of the liver. But not to be too nice here, we proceeded 

 to examine the viscera, concerning which I shall here give some remarks. 



And first, the wind-pipe was different from that of most other animals ; 

 which usually having their cartilages annular, or at least conjoined by a mem- 

 brane, form a fistula for conveying the air into the bronchia; which thence is 

 transmitted into the small bladders of the lungs. But here (fig. 1, aaa) which 

 is common with it to the viper kind, as soon as it enters the breast, presently 

 meeting with the lungs, it consists only of semi-annular cartilages; which being 

 joined at both ends to the membrane of the lungs inwardly is quite open, and 

 immediately transmits the air to the vesiculae of the lungs ; as will better appear 

 by (fig. 4, aaa). For, dividing the wind-pipe, we perceived it easily extended 

 above l^ inch wide ; whereas before it meets with the lungs the cartilages are 

 annular. The trachea or wind-pipe was 20 inches long, terminating near the 

 heart and beginning of the liver, and reaching to that part of the lungs which 

 made the great bladder. The cartilages of the trachea near the beginning were 

 -f- of an inch, but toward the end -l of an inch, and lying fiattish from end to end. 



The use of the trachea is plain, for conveying the air into the lungs; which 

 how considerable an organ they are nature seems to show us by the admirable 

 contrivance and largeness of their structure. They begin from the throat, and 

 run down 3 feet in length. The upper part (fig. 1, b) of them that lay in the 

 forepart of the body for the length of a foot, and reached to the heart, was 

 made of small vesiculae or cells, like the lungs of a frog : but from the frequent 

 branchings and checquers of the blood vessels there, appeared of a florid red. 

 This part tapers proportionably to the body ; the lowest part of it near the heart 

 moderately blown, was in compass 5^- inches; a little lower, for the space of 4 

 inches, the cells gradually disappeared ; so that they seemed at last to form only 

 a reticular compages of valvules conniventes on the inside of the membrane of 

 the lungs ; and the compass of the greatest place here was about 6^ inches ; but 

 from thence to the end of the lungs was only a large bladder (c, c, c, c, c) with- 

 out any cells; composed of a thin but strong transparent membrane, the com- 

 pass of which blown as the former was 8^ inches. 



The lungs of the salamandra aquatica, and some other animals, are only two 

 large bladders. In the frog, crocodile, &c. are two large lobes, filled with 



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