Digestive Organs of the Ox and Sheep. 
29 
The circumstance of some creatures livinir on food which others 
reject has influenced naturalists in placinp: them in different classes. 
Our domestic animals offer a sufficient illustration of this, as 
amonf^ them we find both vesretable and flesh eaters, and also 
those which partake of both these kinds of diet. The horse, ox, 
and sheep are graminivorous ; the dog and cat carnivorous ; but 
the pig is omnivorous. We may also state that in general the 
stomachs are complex in the herbivora; simple in the carnivora; 
and hold a middle position in the omnivora. Many other par- 
ticulars besides the above-named govern the arrangement of ani- 
mals in groups or families, but it is unnecessary to occupy your 
time with an account of them, as a reference to the table (p. oO) will 
show each subdivision. It must, however, be observed that a 
separation of animals into vertebrate and invertebrate is the first 
grand division made by zoologists. The former class includes all 
that possess a chain of bones (vertebrae) extending from the head 
and forming a cavity through which passes the spinal marrow, or a 
continuation of the brain ; the invertebrata are without these 
bones. The second separation consists of those which are furnished 
with mammae, or teats ; and it will be evident that such animals 
bring- forth their young alive — are viviparous, not oviparous: fishes 
and birds thus belong to another class. The mammalia are nu- 
merous, and may be said to inhabit the water, the earth, and the 
air, of which we have examples in the whale, the horse, and the 
bat. All of them are warm-blooded, breathe atmospheric air, 
and possess lungs for the purification of the blood. 
To return to the chief subject of this discourse. It has already 
been stated that digestion commences in the mouth, where im- 
portant changes are effected in the aliment. The way in which 
our different domesticated animals collect their food and convey it 
into this receptacle, first therefore demands our attention. The 
lips, tongue, and incisor teeth are the organs principally employed 
for that purpose, and consequently they are more or less prehensile 
in all. The horse, when feeding on natural herbage, grasps the 
blade with the lips, and by them it is conducted between the 
incisors, which he employs for the double purpose of holding and 
detaching the grass, the latter action being assisted by a twitch of 
the head. The sheep gathers his food in a similar manner, but 
he is enabled to bring his cutting teeth much nearer to the roots 
of the plants, in consequence of the upper lip being partially 
cleft. Hence the adage, that " the sheep will fatten where the 
ox will starve ;" for the upper lip of this animal is thin, and 
possesses considerable mobility; while that of the ox is thick 
and hairless, and has a very limited action. The ox uses the 
tongue to collect his food. The organ, being protruded from the 
mouth, is so directed as to encircle a small bundle of grass, which 
