68 8 NERVOUS SYSTEM. 



is also reflex. Important reflex actions take place through the sympathetic nerves, such 

 as the movements of the intestines, vaso-motor movements, etc. ; but these will be con- 

 sidered fully under the head of the sympathetic system. Secretion, the action of the 

 heart, the contractions of the uterus, the action of the sphincters, the movements of the 

 iris, etc., are regulated by the sympathetic and the cerebro-spinal system. 



As regards the farther action of the cord as a nerve-centre, there are undoubtedly many 

 functions which are influenced more or less by this portion of the cerebro-spinal axis ; but 

 these have been treated of under their appropriate heads or will be considered hereafter. 



CHAPTER XXI. 



THE ENCEPHALIC GANGLIA. 



Physiological divisions of the encephalon Weight of different parts of the brain and of the entire encephalon Some 

 points in the physiological anatomy of the encephalon and its connections The cerebrum General properties of 

 the cerebrum Functions of the cerebrum Extirpation of the cerebrum in the lower animals Pathological facts 

 bearing upon the functions of the cerebrum Comparative development of the cerebrum in the lower animals 

 Development of the cerebrum in different races of men and in different individuals Location of the faculty of artic- 

 ulate language in a restricted portion of the anterior cerebral lobes The cerebellum Some points in the physio- 

 logical anatomy of the cerebellum Course of the fibres in the cerebellum General properties of the cerebellum 

 Functions of the cerebellum Extirpation of the cerebellum in animals Pathological facts bearing upon the func- 

 tions of the cerebellum Connection of the cerebellum with the generative function Development of the cerebel- 

 lum in the lower animals Ganglia at the base of the encephalon Corpora striata Optic thalami Tubercula 

 quadrigemina, or optic lobes Ganglion of the tuber annulare Medulla oblongata Physiological anatomy of the 

 medulla oblongata Functions of the medulla oblongata Connection of the medulla oblongata with respiration- 

 Vital point Connection of the medulla oblongata with various reflex acts Rolling and turning movements fol- 

 lowing injury of certain parts of the encephalon General properties of the peduncles. 



THE anatomy of the encephalon is so complex, that it can be treated of with advan- 

 tage only by a very minute and carefully-illustrated description, such as is to be found in 

 some of the elaborate anatomical works or in special treatises upon the nervous system. 

 We shall not consider under a distinct head the general physiological anatomy of the 

 brain, for the reason just given, and also because we are as yet ignorant of the exact 

 connection between the structure and arrangement of many of its parts and their physi- 

 ology. We know that the gray substance is capable of appreciating general and special 

 impressions received by the peripheral nervous system, and of generating the so-called 

 nerve-force. Impressions are conveyed to this portion of the cerebro-spinal axis by the 

 sensory conductors, passing to the brain, either through the cord or by the cranial 

 nerves, and by the nerves of special sense, as well as those of general sensibility. The 

 stimulus which gives rise to voluntary movements is generated in the brain and is con- 

 veyed by the motor nerves to the appropriate muscles. We have seen, also, that the 

 centres of the encephalon may be concerned in reflex action. In addition, parts of the 

 brain act as centres of sensation and volition and are concerned in the varied phenomena 

 of intellection. 



The encephalon, or what is ordinarily known as the brain, consists of a number of 

 ganglia, or collections of gray matter, connected with each other, and also, by the differ- 

 ent columns of the cord, with the motor and sensory nerves of the general system. Cer- 

 tain of these ganglia have separate and distinct functions which are more or less com- 

 pletely understood ; while there are, in addition, masses of gray substance, the physio- 

 logical relations of which are as yet obscure or entirely unknown. The greatest and 

 the most important of all, the gray matter of the cerebral hemispheres, undoubtedly has 

 subdivisions connected with distinct attributes of the mind ; but our positive knowledge 

 with regard to these divisions is, at the present day, very meagre, although this subject 

 has long been a favorite field for philosophical speculation. 



Confining ourselves strictly to the limits of positive information, we may recognize 



