814 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



in an apparent condition of almost total paralysis, yet after the shock of 

 the operation has passed off a number of highly complex reflex motions 

 may be evoked. If, however, the section of the cord be made at the 

 anterior border of the medulla the position of the frog after the shock of 

 the operation has passed off is more nearly normal, and allusion has been 



Thai: 



a be de fa 



vvv 



V S H 



Fig. 353.— Diagram of the Chief Tracts 

 in the Medulla, after Erb. 

 (Ranney.) 

 The formatio reticularis is represented by shading. 

 01., olivary body ; V anterior, S lateral, and H pos- 

 terior spinal funiculi; a, pyramido-anterior tract; d, 

 pyramido-lateral tract ; Py., pyramidal tract ; b, re- 

 mainder of anterior column : r, remainder of the lateral 

 column: e, e., cerebello-lateral tract; /, *funioulus gra- 

 cilis, and,./', nucleus of the same; g, funiculus cunea- 

 tus, and, g>, nucleus of the same; P.c.L, internal 

 fasciculus of the pedunc. cerebelli ; P.c.e., external 

 fasciculus of the same; Cq.F., tract from corp. quadr. 

 to format, retic; Cq.O., the same to the olivary body; 

 Thai., tract from the thalamus opticus. 



Fig. 354.— Transparent Lateral View 

 of the Medulla, showing the 

 Relative Positions of the Most 

 Important Nuclei; Right Half 

 of the Medulla, Seen from the 

 Surface of Section; The Parts 

 that Lie Closer to this Surface 

 are Deeper Shaded, after Erb. 

 {Ranney.) 

 Pi/, pyramidal tract; Py. Kr, decussation of pyramids; 



0. olivary body; O.-s superior olivary body; V, motor, 



VI, middle sensory. F", inferior sensory nucleus of 

 trigeminus; VI. nucleus of abducens ; <?./, genu facialis ; 



VII. nucleus facialis; VIII. posterior median acoustic 

 nucleus ; IX, glosso-pharyngeal nucleus X, nucleus of 

 vagus; XI, accessorius nucleus; XII, hypoglossal nu- 

 cleus; K.z, nucleus of the funiculus gracilis; RV, tri- 

 geminus roots ; those of the R VI, abducens, and RVII, 

 facialis. 



made to the fact that in the mid-brain is seated a centre which inhibits 

 reflex action. 



When the cerebral lobes only have been removed in the frog, volition 

 is apparently the only function of the animal which is wanting, and in 

 the absence of stimuli of all characters the animal remains absolutely 

 inert. If such a frog is thrown into water it swims ; by stimulating its 



