xvn. EELS AND ELVERS. 239 



on so unpromising a substance, but place him for a minute 

 or two in a glass tube, that we may examine him with a 

 magnifying glass. Just behind the gill-chambers and, the 

 pectoral fins, the dark red heart may now be seen, beating 

 regularly and uniformly. This consists of two chambers, 

 the ventricle in front, and the auricle behind ; and it is 

 quite easy to see that the auricle, which is the receiver of 

 blood coming from the various parts of the body, beats a 

 little in advance of the ventricle, which is the force-pump 

 driving blood through the arteries to supply the various 

 organs with nutrient fluid. And as the ventricle contracts 

 it becomes pale, from the fact that the blood is all driven 

 out of it. One can trace, with a little care, the artery 

 which carries this blood forward to the 'base of the gill- 

 arches. It thus passes into the gills, where it is oxygenated 

 and purified, and collecting into vessels above them is 

 carried, some of it forward to the head, some of it backward 

 beneath the back-bone to supply the body. 



Those who know something of their own hearts (I mean 

 from the anatomical point of view) may be surprised that 

 the elver should have only one auricle (or receiver) and one 

 ventricle (or force-pump) ; for the heart of man has two of 

 each. But we must remember that man's double heart 

 (again I speak anatomically ; it is the same with the guile- 

 less monkey) is closely associated with the possession of 

 lungs, the right ventricle forcing the blood into these 

 organs, the left auricle receiving the pure rich blood which 

 returns from them, handing it on to the left ventricle, 

 which forces it throughout the body to be re-collected in 

 the right auricle before proceeding again to the lungs. In 

 the fish there are no lungs, and the double-heart system is 

 wanting. 



Behind the pulsating heart lies the pinkish liver. But 

 no doubt by this time the delicate reader thinks that I 



