Ray Lankester, on the Tooth in Ziphius Sower biensis. 55 
the lung should be touched as little as possible, and in the 
lightest manner, with the brush. If the heart is acting feebly 
you will see simply a transparent sac, shaped according to 
the quantity of air-bubbles it may happen to contain, but void 
of red vascularity and circulation, as in the left lung of fig. 15. 
But should the operator succeed in getting the lung well 
placed, full of air, and have the heart still beating vigorously, 
he will see before him a brilliant picture of crimson network, 
alive with the dance and dazzle of blood-globules, in rapid 
chase of one another through this delicate and living lacework 
which lines the chamber of the lung (fig. 15). The trunk 
of the pulmonary artery is conspicuous on the one side as the 
channel which brings the blood to the lung, and the ramifi- 
cations of which constitute the fine network aforesaid, while 
the pulmonary vein on the other side returns the aerated 
blood to the heart. The internal surface of the lung becomes, 
in the older frog, developed into numerous shallow cells, the 
boundaries of which correspond to the polygonal facets pre- 
sented by the external surface. 
Fig. 16 is the drawing of a dissection made to exhibit the 
trunks of the systemic arteries in the frog, with the origins of 
the pulmonary arteries and the course of the pulmonary 
veins, in the full-grown reptile. 
Permit me, in conclusion, to thank you for the gracious 
and liberal manner in which you have enabled me to present 
the results of my humble labours on this interesting subject 
to the members of this society. 
On the Structure of the Tooth in Ziphius Sowerbiensis 
(Micropteron Sowerbiensis, Eschricht), and on some 
Fossil Cetacean Teeth. By E. Ray Lankester, 
F.R.M.S. of Christ Church, Oxford. 
(Read May 8th, 1867.) 
If it be true that “ differences in structural arrangement 
which exist without our being able to see why they should 
exist possess a morphological value which rises in direct 
proportion with their physiological obscurity,”* the teeth of 
the Ziphioid Cetaceans have a very considerable claim on the 
interest and attention of zoologists. The “ reason why ” a 
Cetacean should have two powerful teeth in its lower jaw— 
apparently incapable of biting, or curved over the top of its 
* Professor Rolleston, ‘Trans. Zool. Society,’ vol. v. part 4, p. 311. 
