Respiration, possessed by AquaticMammalia and Birds. 127 



numerous individuals of the two species of seal [Phoca harhata 

 and P. vitiilina) which I have dissected, I have never found 

 it open, but in foetuses. But secondly, though this were the 

 fact, it affords no solution of the question, — of the faculty which 

 these animals possess of supporting life, not merely like the 

 foetus, with the external senses dormant, and supplied with 

 oxygenated blood through the medium of the mother, but in 

 all the play and vigour of their faculties, without the action of 

 the lungs or the access of oxygen. The forajnen ovale re- 

 maining open may cause less blood to circulate through the 

 lungs, and more to be thrown on other organs ; but the fact by 

 no means accounts for the animal being able to sustain vigor- 

 ous and perfect life, while venous blood must be circulating 

 through the brain, and the vital function of respiration totally 

 interrupted. If it be conceded that provisions may be found, 

 in the increased size of the liver, spleen, or veins of the ab- 

 dominal viscera, for receiving an additional quantity of blood, 

 diverted from the lungs during the suspension of respiration, 

 still this points out only a change in the distribution of the 

 circulating fluid. 



It can hardly be assumed that the moment the animal dives, 

 those processes, which exhaust the blood of its oxygen, are 

 interrupted ; for still, at the moment of suspending respiration, 

 much venous blood must necessarily be existing in the circu- 

 lation. And can we suppose that, until respiration is renewed, 

 the venous blood remains in the pulmonic system without be- 

 ing carried to the systemic heart? Such a hypothesis, not 

 more visionary than some others, only, like them, multiplies 

 difficulties ; it supposes, for instance, a power of suspending 

 the processes which exhaust the blood of those vivifying prin- 

 ciples which it receives from respiration. It supposes the pul- 

 monic and systemic hearts to be, not merely in function dif- 

 ferent, but in action separate from and independent of each 

 other. It presumes that the left ventricle contracts on vacuity, 

 or that the aorta and its tributaries can, at the will of the ani- 

 mal, become substitutes for the action of the heart. 



Can we assume, that some other organ is vicarious of the 

 function of the lungs, analogous to what we observe to a cer- 

 tain extent to obtain in some secretory functions, as those of 

 the skin and kidneys; or that the system enjoys the power of 

 accumulating an additional stock of oxygen to supply its diving 

 exigencies? Or can we imagine that the liver or any other 

 organ deprives in a great measure the venous blood of those 

 qualities which render it so deleterious to life in terrestrial 

 animals, when carried through the arteries to the brain, as the 

 experiments of Bichat especially, and of other eminent phy- 

 siologists 



