THE CIRCULATIOK OP THE BLOOD. 



217 



It will be found very helpful to perform some of the dissec- 

 tions under water, and by the use of this or some other fluid 

 the action of the valves may be learned as it can in no other 

 way. By a little manipulation the heart may be so held that 

 water may be poured into the oriiices, prepared by a removal 

 of a portion of the blood-vessels or the auricles, when the valves 

 may be seen closing together, and thus revealing their action in 

 a way which no verbal or pictorial representation can do at all 

 adequately. 



A heart thoroughly boiled and allowed to get cold shows, on 

 being pulled somewhat apart, the course, attachment, and other 



BAV 



Flo. 187.--View of the orifices of the heart-from below, the whole of the ventricles 

 having been cut away (after Huxley). RAY, right auricalo-ventricnlar orifice, 

 surrounded by the three fiaps. t,vA^ t. v. 2, t. v. 3, of the tricuspid valve, which are 

 stretched by weights attached to the chordm tendinece. LAV, left auricnlo-ven- 

 tricular orifice, etc. PA, orifice of the pulmonary artery, the semilunar valves 

 represented as having met and closed together, AP, orifice of the aorta. 



features of the fibers very well, as also the skeleton of the organ, 

 which may be readily separated. 



When this has all been done, the half is not yet accom- 

 plished. A visit to an abattoir will now repay amply for the 

 time spent. Animals are there killed and eviscerated so rapidly 

 that an observer may not only gain a good practical acquaint- 

 ance with the relations of the heart to other parts, but may 

 often see the organ still living and exemplifying that action 



