INSECTS
With the conditions of living granted, however, protoplasm is still only potentially alive, for there is yet required a stimulus to set it into activity. The stimulus for life activities comes from changes in the physical forms of energy that surround or infringe upon the potentially living substance; for, "live" matter, like all other matter, is subject to the law of inertia, which decrees that it must remain at rest until motion is imparted to it by other
Fig. 66. The head and mouth parts of a grasshopper
A, facial view of the head, showing the positions of the antennae (Ant), the large compound eyes (E), the simple eyes, or ocelli (O), the broad front lip, or labrum (Lm) suspended from the cranium by the clypeus (Clp), and the bases of the mandibles (Md, Md) closed behind the labrum
B, the mouth parts separated from the head in relative positions, seen from in front: Hphy, hypopharynx, or tongue, attached to base of labium; Lb, labium; Lm, labrum; Md, mandibles; Mx, maxillae
motion. A very small degree of stimulating energy, however, may result in the release of a great quantity of stored energy.
The food of all living matter must contain carbon, hydrogen, nitrogen, and oxygen. The mechanism of plants enables them to take these elements from compounds dissolved in the water of the soil. Animals must get them from other living things, or from the products of
[106]
