PROFESSOR SPOONER’S ORATION. 
737 
ing teeth as in the horse, and, even to a greater extent — tiie 
lateral action of the lower jaw implying to a certainty that 
these animals also must subject their food to much mastication. 
Nevertheless, if from these isolated facts we were to draw the 
same inference with regard to deglutition that we have done in 
the horse, a farther knowledge of the anatomy and general eco- 
nomy of ruminants would prove to us that we were wrong. 
It would develop to us the singular fact, that they first swallow 
their food in a very rough state, and that, subsequently, in ac- 
cordance with the will, it is again passed up into the mouth, 
where it undergoes the process of re-mastication. For additional 
peculiarities in these parts, I will briefly refer you to the dog, 
and we shall perceive that in him — a carnivorous animal — there 
is an absence of the prehensile function of the lips: yet, being 
endowed with a great capacity of mouth, and immense muscular 
power in opening and closing it, aided by the strength and posi- 
tion of the teeth, the protrusive agency of the tongue, and the 
grasping power of the fore extremity, he is readily enabled to 
supply himself with such food as is best suited for his sustenance 
and support. From the fact of the grinding surfaces of the 
molar teeth and the lateral movement of the lower jaw being 
altogether wanting, we can to a certainty state that the pro- 
cess of mastication must be in him — as compared with the two 
former classes of animals — extremely limited ; while on the other 
hand, in the pig, which is omnivorous, the structure and func- 
tion of these organs will be found to hold a medium state of de- 
velopment, and we are thus forcibly struck with their beautiful 
adaptation to the variety of food upon which he subsists. 
Pursuing this subject, we will now, with your permission, 
take a hasty glance at that division of the alimentary canal which 
is situated in the cavity of the abdomen ; and we shall see that it 
presents to us a somewhat complicated arrangement, varying in 
its length in different animals, and especially so in the general 
capacity and internal structure of the respective organs that 
enter into its formation. In every part of this canal it is described 
as being made up of three distinct tissues, placed the one over the 
other — the outer layer being the peritoneum, under which is situ- 
ated the muscular coat, while, within, it is lined with mucous 
membrane. It is to this last named structure that I shall more 
especially allude. 
The term mucous membrane is applied to that tissue which 
lines the inner surfaces of all those passages that have communi- 
cation with external outlets ; and when speaking of it as con- 
nected with the mouth, the stomach, the bladder, or the lungs, 
you might suppose that it was the same in structure, the same 
VOL. xiv. 5 E 
