384 Swimming of Snakes. 



cellular tissue presents, when cut into, a series of close, deli- 

 cate, and beautiful reticulations. These meshes gradually en- 

 large, till the whole of the lower part of the lungs consists of 

 large cancelli, the membrane being extremely thin, and semi- 

 transparent. It is, most probably, only in the upper portion 

 of the lungs that the blood undergoes the change resulting 

 from its contact with atmospheric air ; and it is to be ob- 

 served, that the vascular system of this upper and finely 

 reticulated part is such as to favour this idea, which, if cor- 

 rect, would lead to the conclusion that the lower portion of 

 these organs served exclusively as a reservoir for air. I have 

 often, on inflating the lungs of a snake, been surprised at the 

 volume of the lower portion, and the quantity of air it is 

 capable of receiving ; and I am inclined to believe that the 

 lungs, when filled, are capable of containing a volume of air 

 which will serve the system for a considerable time, the ne- 

 cessity of taking in a fresh supply every instant, as do Mam- 

 malia and birds, being obviated. Snakes have often been 

 seen in such a situation as to prevent, for a certain period, 

 the power of respiration. We know that they swallow their 

 prey whole ; and that a portion of their victim, too large to be 

 gorged at once, distending their jaws to the utmost, and com- 

 pressing the larynx, often projects out of their mouth, and so 

 remains, till, as the part in the stomach digests, the remainder 

 passes gradually down. Our common snake will swallow a 

 large frog or rat ; a boa of moderate size will swallow a goat 

 or antelope ; and I do not see how the larynx and trachea can 

 avoid being compressed during the act of gorging the bodies 

 truded, the tube of the trachea will suffer, and respiration be thus 

 of animals of such disproportionate bulk. If the larynx be pro- 

 effectually prevented : consequently, the supposition that the 

 protrusion of the larynx suffices to this operation, is nugatory. 

 Besides, is the larynx protruded ? this is a point in abeyance. 

 Without pretending to settle this question, it may be re- 

 marked, that the unvitiated air, contained in what I regard as 

 the reservoir portion of the lungs, will suffice for some time 

 at least (and the length of time is yet to be determined) to 

 oxygenise the blood in the upper or true portion of the lungs, 

 while respiration is interrupted ; and as, in the case alluded 

 to, respiration must, I think, be admitted to suffer interrup- 

 tion, the necessity of this reservoir becomes apparent. The 

 following fact seems to confirm these views : — Some years 

 since, passing by a small sheet of water, near Bakewell, on the 

 Buxton road, I observed a snake quietly swimming towards 

 the bank. I hastened to the spot for which he was making. 

 On seeing me he stopped, and allowed himself to sink gently 



