. The evolution and function of living purposive matter . animal sofar as its sensoryorgans and centralnervous system areconcerned. Fig. 11 representsa section madethrough the brain ofone of these animalsmagnified 50 diame-ters, it gives an ideaof the complex ar-rangement of thenervous structuresentering into theformation of a cray-fishs brain. FiQ. 10.—i)»agi)am of nervous system of a Chseto- Tf io t-n \\a r\r\+inckApod. B, brain; en, cephalic nerves to supply il; IS WJ ue uui/ioeu sense organs of anterior end of the worm; nc, ,„4. ,„ riorirpo rrrn nerve cord passing from the brain to s
. The evolution and function of living purposive matter . animal sofar as its sensoryorgans and centralnervous system areconcerned. Fig. 11 representsa section madethrough the brain ofone of these animalsmagnified 50 diame-ters, it gives an ideaof the complex ar-rangement of thenervous structuresentering into theformation of a cray-fishs brain. FiQ. 10.—i)»agi)am of nervous system of a Chseto- Tf io t-n \\a r\r\+inckApod. B, brain; en, cephalic nerves to supply il; IS WJ ue uui/ioeu sense organs of anterior end of the worm; nc, ,„4. ,„ riorirpo rrrn nerve cord passing from the brain to seg, the if giving off nerves to the corresponding segments of ^^^^^aiig xxuxxi uxic ^^^°^^- animals eyes and from its olfactory sensory organs terminate in thenervous substance of the middle segment of thebrain. In this area of the brain two descriptionsof nerve cells may be recognised in some of thelarger Crustacea, the one set of cells are of small size. INTO SENSORY AND MOTOK CELLS 41 and polygonal in form, the other are large pyramidalcells; the former we recognise as constituting thesensory receptive station for afferent or incoming energypassing to it from the sensory organs. The largepyramidal cells we have reason to hold contain themotory elements from which energy is despatched tothe muscles of the animals body. This part of thebrain therefore corresponds with that which in thehigher classes of animals is known as the basal gangha.^This area of the brain constitutes the central stationfor lines of communication passing from the principalsensory organs of the animals head and body, and itsoffice is to co-ordinate this energy and direct it intoforms of activity calculated to promote the well-beingof the organism. It will be noticed on referring to the figure that thefungiform matter (GN, ganglionic nuclei of Fig. 11)is more highly developed in the cra)^sh than it is inthe brain of the sea-mouse, and that it passes
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Keywords: ., bookcentury1900, bookdec, booksubjectbrain, booksubjectphysiology
