XVI 



SUPPORT, MOTION, AND SENSATION 



Preview. Section A. Skeletal devices • The interdependence of 

 parts • The kinds of skeletons : Exoskeletons ; endoskeletons ; the axial 

 skeleton ; the appendicular skeleton • Functions of skeletons : Support ; 

 protection; movement • Section B. Devices for movement • The "why" 

 of motion and locomotion ; protoplasmic extensions ; demio-muscular 

 sacs ; water vascular systems • Muscles and muscular systems : Smooth 

 or involuntary muscles, skeletal or striated muscles, heart muscle, muscular 

 contractions • Section C. Mechanisms of sensation and co-ordination • 

 The morphological unit — The neuron • The physiological unit — The 

 reflex arc • Types of nervous systems : Neuromotor mechanisms ; co-ordina- 

 tion by a network ; co-ordination by a nerve ring ; co-ordination by a linear 

 nervous system ; co-ordination by a dorsal tubular nervous system • Pro- 

 tective devices for the central nervous system • Anatomy and development 

 of the brain : The early development of the central nervous system ; the 

 parts of the vertebrate brain : The cerebrum or telencephalon, the 'Twixt- 

 brain or diencephalon, the mid-brain or mesencephalon, the cerebellum or 

 metencephalon, the medulla oblongata or myelencephalon ■ The cranial 

 nerves • The spinal cord ■ The spinal nerves • The autonomic nervous 

 system • The sense organs — Receptor devices : taste ; smell ; simple light 

 receptors ; compound eyes ; camera eyes ; ears ; cutaneous sense organs • 

 Suggested readings. 



PREVIEW 



It will be seen from the preceding unit that one of the most impor- 

 tant essentials for an animal is to carry on successfully its metabolic 

 processes. This is equally necessary for plants although they have 

 the advantage of being able to secure most of the raw food materials 

 they need from their immediate environment. Animals have to 

 move to get their food. The necessity for motion involves three 

 factors, a mechanism to support the body when seeking food, 

 machinery to do the moving, and an apparatus to detect the location 

 of food. In order to locate food, a co-ordination of eye and Hmb 

 under control of the nervous system is required. The eye receives a 

 stimulus the instant that the color or shape of food is noted by the 

 receptor devices in the retina. The motions of the arms and legs then 

 supplement the desire for food, followed by the act of taking it. In 



326 



