R E S I : ARCHES 



UPON THB 



ANATOMY AND PHYSIOLOGY OF RESPIRATION IN THE CHELONIA. 



CHAPTER I. 



In the whole animal series there is scarcely a creature that would he less likely 

 to suggest itself as a held for discovery than the Turtle. Its temptingly curious 

 form, its world-wide distribution, its limited means of escape and of defence, would 

 seem to combine to render it an easy and early object of investigation to the 

 naturalist. And yet the history of Chelonians is Ml of discordant observations; 

 functions have been misinterpreted, and even important parts of structure have been 

 asserted to exist by some, and again denied by others, until at the present day the 

 uncertain record has forced opinion into error, and permitted the conduct of one of 

 the most important processes of life, that of respiration, to remain misunderstood, 

 and the means of its accomplishment neglected and in part unknown. The view 

 now entertained by the leading authorities upon the subject, that Turtles inspire 

 by an act of deglutition, as do the frogs, has prevailed from the first, and doubtless 

 arose from the panting movements of the under part of the throat, common to both 

 orders, and among turtles, especially observable in marine species. It will be the 

 object of this paper to show that this view is incorrect, that turtles do not swallow 

 the air in breathing, but that their respiratory act is effected by inspiratory and 

 expiratory muscles situated within the trunk. 



The solid thorax clearly indicates that Chelonians do not enjoy the perfect 

 respiratory mechanism of the highest vertebrates. The ordinary tranquil respiration 

 of mammals, when the ribs are at rest and the cavity of the thorax is enlarged by 

 the descent of the diaphragm alone, is, however, very strikingly analogous to that of 

 turtles, in which the cavity of the shield is enlarged by the .contraction of the muscles 

 of the flanks. 



In tracing the anatomical history of the organs of respiration in Chelonians, the 

 earliest work to which we have had access is a "Dissertation on the Respiration of 

 the Tortoise," by Robert Townson, LL. D., written at Gottingen, May, 1795; and 

 as we find in it a brief review of all that was known previously upon the subject, 

 we have taken the privilege of embodying this rare and interesting paper in the 

 present sketch. This we do more cheerfully as an act of justice to the author; for, 

 having conducted our inquiry with a full knowledge of the opinions of modern 



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