1881.] NATURAL SCIENCES OF PHILADELPHIA, 137 



the biain and cord and upper extremities to the heart, that from 

 the viscera and lower extremities can be entii'ely cut off from it, 

 welling back into the dilated cava and cutaneous veins, while 

 congestion of the brain can be prevented when the animal sinks 

 under water by the obliteration of the carotid arteries. In this 

 way paralysis of the respiratory centres of the brain and cord 

 through congestion is prevented, while the demand for fresh air 

 is diminished, so much blood being retained in the viscera and 

 lower extremities and so diverted from the lungs. Tliese pecu- 

 liarities in the vascular system of the Hippopotamus — taken 

 together with the disposition of the nares, larynx, etc., already 

 referred to, through which the air can be retained — accounts, 

 according to Gratiolet,' for the Hippopotamus being able to 

 remain under water for so long a time, from fifteen to even forty 

 minutes. 



Bert,- while admitting the force of Gratiolet's reasoning, attrib- 

 utes the power that many animals have of resisting for a long time 

 asphyxia, however produced, rather to the relative richness of blood 

 that is contained in their bodies ; the blood serving as a storehouse 

 or magazine for oxygen which cS,n be drawn upon when needed. 

 For example, Bert has shown that the blood of the duck is richer 

 than that of the chicken, and explains in this way that the duck 

 will live longer than the chicken, when both are asphj^xiated either 

 by submersion in water or by ligation of the trachea. It seems to 

 me, however, that the great quantity of blood present in those 

 mammals that are in the habit of remaining under the water any 

 length of time is an important element in the question. In open- 

 ing several sea-lions, Zalophus Gillespii, that have died at the 

 Zoological Garden, and different Cetacea, I have been alwa3^s im- 

 pressed with the enormous quantity of blood that literally ran out 

 of their bodies. In presenting a specimen of a Dolphin, Ddphi- 

 nus^ to the Academy, I called attention^ to the vast rete mirabile 

 formed by the intercostal arteries constituting the intercostal 

 gland of the older anatomists, and which is usually regarded as a 

 reservoir of arterialized oxygenated blood, to be drawn upon ac- 

 cording to the needs of the animal. If the blood of the seals and 

 cetaceans proves to be relatively richer than that of othei" mammals, 



1 Recherches, p. 363. 



- Physiologie comparie de la Respiration, p. 543. 



' Proceediugs of Academy, 1873, p. 279. 



