ANATOMY OF THE BEAVER. 75 



one animal it was 3i" in length, in another, 41", with 

 an average width of 40'". Weight of the largest spleen, 

 110 grains. 



The right lung has two lobes, one of them bifid. 

 The left lung has four lobes. The supra-renal cap- 

 sules in the rodents are relatively large. The kid- 

 neys present nothing remarkable. Weight of one 

 kidney 640 grains. The heart weighs 714 grains, 

 and resembles the human in its cavities, valves, ves- 

 sels, etc. In one beaver a large calcareous deposit ex- 

 isted above the aortic valves. In another there was 

 incipient atheroma in patches in the same situation. 



M. Sarrasin, in his account of the beaver, describing 

 the heart, says the right auricle being smaller than the 

 left, the right ventricle is filled by the conjoint action 

 of the auricle and the vena cava inferior; the latter 

 being at this point considerably expanded. The venous 

 sac, he adds, is narrower by the side of the liver where 

 it is closed by three valves, like the sigmoidal, which 

 prevent the reflux of the blood during the act in 

 question. M. Sarrasin's account of the beaver is so 

 generally correct that his misconception on this point 

 is the more remarkable. It is well known that in 

 diving animals, whether birds or mammals, a provi- 

 sion exists in the venous system against the evils of 

 suspended respiration. R. Knox, Esq., claims to have 

 first noticed it in the case of the beaver. His account 

 is contained in the Memoirs of the Wernerian So- 

 ciety, vol. iv., part ii., 1823. This provision consists 

 in an enlargement of the inferior vena cava as it 

 passes through the fissure of the liver, constituting a 

 sinus in which a considerable quantity of blood may 

 be temporarily arrested. 



