Elementary anatomy and physiology Elementary anatomy and physiology : for colleges, academies, and other schools elementaryanato00hitc Year: 1869 AND PHYSIOLOGY. 363 may be called a brain. In Insects ' the central parts of the nervous system con- sist of a brain and a ven- tral cord,'7 as is shown on Fig. 336. In some of the lower tribes of Articulates, as the Helminthes and Rota- toria, the nervous system is feebly and indistinctly de- veloped. 668. Reflex Actions in Ar- ticulates. — This sub-king- dom is remarkable for its reflex actions. Thus if the head of a centipede be cut off while it
Elementary anatomy and physiology Elementary anatomy and physiology : for colleges, academies, and other schools elementaryanato00hitc Year: 1869 AND PHYSIOLOGY. 363 may be called a brain. In Insects ' the central parts of the nervous system con- sist of a brain and a ven- tral cord,'7 as is shown on Fig. 336. In some of the lower tribes of Articulates, as the Helminthes and Rota- toria, the nervous system is feebly and indistinctly de- veloped. 668. Reflex Actions in Ar- ticulates. — This sub-king- dom is remarkable for its reflex actions. Thus if the head of a centipede be cut off while it is in motion, the body will con- tinue to move by the action of its legs; and the same will take place, if the body is divided into several segments. The explanation is as follows. 'The body is moved forward by the regular and successive action of its legs, as in the natural state : but its movements are always forwards, never back- wards, and are only directed to one side, when the forward movement is checked by an interposed obstacle. Hence, al- though they might seem to indicate consciousness and a guid- ing will, they do not so in reality: for they are carried on as it were mechanically, and show no direction or object, no avoidance of danger. If the body be opposed in its progress by an object of not more than half its height, it mounts over it, and moves directly onwards, as in its natural state : but if the obstacle be equal to its own height, its progress is ar- rested, and the cut extremity of the body remains forced up against the opposing substance, the legs still continuing to moveP Fig. 336. Nervous System of a Beetle. What is the name of the principal ganglia? 668. What is sai:i of the reflex actions of articulate animals ? What are these reflex actions somttimes mistaken for* Giva the example.
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