PHYSIOLOGICAL DIVISIONS OF THE ENCEPHALON. 601 



The gray matter of the cord is not a single centre, but consists of a num- 

 ber of centres connected with each other and with the brain. Some of these 

 have already been described in connection with the history of various physi- 

 ological processes, and others will be considered hereafter under appropriate 

 heads. In addition to those already described, are centres for defsecation, at 

 the fifth lumbar vertebra in dogs (Budge), the erection-centre, in the lumbar 

 region (Eckhard), and the parturition-centre (Korner), at the first and sec- 

 ond lumbar vertebrae. All of the spinal centres act in accordance with the 

 general laws of reflex phenomena. 



CHAPTER XIX. 



THE ENCEPHALIC GANGLIA. 



Physiological divisions of the encephalon Weights of the encephalon and of certain of its parts The 

 cerebral hemispheres Cerebral Convolutions Basal ganglia Corpora striata, optic thalami and inter- 

 nal capsule Tubercular quadrigemina Pons Varolii Directions of the fibres in the cerebrum Cere- 

 bral localization General uses of the cerebrum Extirpation of the cerebrum Facial angle Pathologi- 

 cal observations Reaction-time Centre for the expression of ideas in language The cerebellum 

 Physiological anatomy Extirpation of the cerebellum Pathological observations Connection of the 

 cerebellum with the generative function Medulla oblongata (Bulb) Physiological anatomy Uses of 

 the medulla oblongata Respiratory nerve-centre Cardiac centres Vital point (so called) Rolling and 

 turning movements following injury of certain parts of the encephalon. 



THE encephalic ganglia are collections of gray matter found in the en- 

 cephalon, or what is commonly known as the brain. This part of the cerebro- 

 spinal axis is situated in the cranial cavity. It is provided with membranes, 

 which are similar to the membranes of the spinal cord and have been de- 

 scribed in connection with the cord and the general arrangement of the cere- 

 bro-spinal axis. The gross anatomical divisions of the encephalon are the 

 cerebrum, cerebellum, pons Varolii and medulla oblongata. As regards their 

 physiological uses, the cerebellum, pons and medulla are to a certain extent 

 subordinate to the cerebrum. In treating of the physiology of these parts, 

 it will be convenient to take up first the cerebrum, or the cerebral hemi- 

 spheres, with their anatomical and physiological connections and their rela- 

 tions to the other parts of the encephalon. 



All parts of the encephalon which act as nerve-centres are more or less 

 intimately connected with each other anatomically, and are finally connected, 

 through the medulla oblongata, with the spinal cord. The exceptions to this 

 rule are the centres of olfaction, vision, audition and gustation, which will 

 be considered fully in connection with the physiology of the special senses. 

 The spinal cord, as has been seen, is capable of independent action as a 

 nerve-centre or collection of nerve-centres, also serving as a means of connec- 

 tion between the brain and the parts, through the spinal nerves. The motor 

 and sensory cranial nerves are directly connected with the encephalon. 



A detailed anatomical description of the brain would be out of place in 



