Section of Medical Science, 503 



these animals while under water, there is another cause operating, 

 when at great depths in the ocean, to the prejudice of their circu- 

 lating fluids, such as is never experienced by terrestrial animals, 

 namely, pressure on the surface of their bodies by the water, increas- 

 ing with the depth from the surface. A boat, as observed by Scoresby, 

 when dragged to the bottom of the sea by a whale, into which a har- 

 poon was struck, became in a few minutes as completely soaked in 

 every pore as if it had lain at the bottom of the sea since the flood : 

 after being raised again to the surface, by the whale returning " to 

 blow", it could with difficulty be got into the ship on account of 

 its great weight ; and a fragment of it, when thrown into the sea, 

 sank to the bottom like a stone. And are we to suppose that a de- 

 gree of pressure under water, sufficient to soak in an instant every 

 pore in the planks of a large boat, was not felt by the animal which 

 dragged it to such a depth ? There can be little doubt that the 

 application of this pressure would repel the fluids from the vessels 

 near the surface of the animal into those more removed from its in- 

 fluence in the deeper recesses of its body ; that, in fact, an effect 

 would follow, the opposite of that which is produced in an animal 

 when placed under the exhausted receiver of an air-pump ; or such 

 as occurs in persons attaining so high an elevation in the atmosphere 

 as to be freed from some of its weight, in whom the blood is deter- 

 mined to the surface, producing giddiness, bleeding from the nose, 

 ears, lungs, &c. 



We may consider, therefore, that aquatic mammalia can exist with 

 impunity during periods of suspended respiration, and also under 

 degrees of pressure which would be destructive to the lives of ani- 

 mals of the same class whose element is exclusively the atmosphere. 

 And this may be considered still more remarkable, when it is recol- 

 lected that during those periods of breathlessness and universal pres- 

 sure, the voluntary and rapid movements which these animals perform 

 when in pursuit of their prey, tend to urge towards the lungs, where 

 the principal obstruction exists, all the fluids contained in the veins 

 among the muscular structures of the body. 



The object of Dr. Houston's communication is to point out the 

 provision on which these peculiar diving faculties of such animals 

 depend ; a provision beautifully harmonizing with all our physiolo- 

 gical notions, and admirably adapted to the end in view. It consists 

 of reservoirs connected with the veins leading to the lungs, where 

 the blood may find a temporary resting-place during the period at 

 which the asphyxiated condition of these organs refuses it transmis- 

 sion through the vessels. Dr. Houston exhibited numerous prepara- 

 tions and drawings demonstrating the presence of this singular 

 provision in the porpoise, seal, otter, great northern diver, gannet, 

 &c. The veins principally concerned in these dilatations are those 

 nearest the heart, viz. the venae cava?, the venae cavae hepaticae, the 

 jugulars, the veins of the spine, and those in the posterior regions of 

 the abdomen. In the seal the venae hepaticae form large bags in the 

 liver ; and in the same animal there is on the back, and along the 

 sides, and posterior part of the neck, a plexus of veins of such size, 



