Journal of Agriculture. [lo Dec, 1908. 



entering higher up in the brain-stem make connection with this region by 

 ■circuitous routes. The motor outflow proceeds to the muscles that move 

 •the tongue — by the 12th; all the muscles of the larynx except one — by 

 the nth; the muscles of the jaws — by the 5th; the muscles of the face — 

 by the 7th ; the muscles of the soft palate and the pharynx and one 

 muscle of the larnyx — by the 9th ; and the external (posterior) rectus 

 muscle of the eyeball — by the 6th. The autonomic outflow is very con- 

 siderable and includes inhibitory to the heart, secretory to the glands 

 of the stomach, motor to the smooth muscles of the alimentary canal from 

 the ce.sophagus to the first part of the colon — these pass out by the 

 J oth ; secretory to the salivary glands and the glands of the mouth 

 by the 7th and 9th. Perhaps the most remarkable feature of the medulla 

 is the number of centres for various visceral reflexes which it contains — 

 there are, for example, centres for the heart movements, for arterial 

 constriction, for respiration, swallowing, vomiting, secretion of saliva and 

 regulation of temperature. The pons contains the centre for closure of the 

 eyelids on irritation of the cornea or strong illumination. 



The CEREBELLUM may be regarded as a great expansion of the brain- 

 stem connected with the proprioceptive system. It has a peculiar laminated 

 structure with grey matter external and white matter within. Into it 

 stream branch fibres from the nerves coming from the semi-circular canals 

 and from the afferents of tho.se muscles, tendons and joints that are 

 concerned with body movement and posture From the cerebellum nerve 

 fibres pass to the brain-stem and particularly to the spinal cord. If the 

 cerebellum be injured, the animal moves in a peculiar reeling or drunken 

 manner or, if the injury be a serious one, may spin round or turn 

 somersaults with considerable violence. The tautness or "tone" of the 

 various muscles of the body not actually in active contraction is partly 

 attributable to cerebellar influence. 



The region of the corpora quadrigemina receives scarcely any afferent 

 fibres directly. It has a small motor outflow to the superior oblique 

 mu.scle of the eyeball by the 4th cranial or trocJilear, and to all the other 

 muscles of the eyeball (except the posterior or external rectus) by the 3rd 

 jcranial or oculo-motor. The autonomic outflow occurs via the 3rd nerve 

 and has to do with the ciliary muscle of the eye and the constrictor 

 muscle of the iris. This region contains centres for the adjustment of the 

 pupil to varying strengths of light, for phonation, for quadrupedal pro- 

 gression, and for sneezing. 



The region of the thalumus is that portion of the brain-.stem where 

 branch fibres from all the afferents of true sensation entering the central 

 nervous system meet and then form new relays that spread into the fore- 

 brain. A si>ecial protrusion of the thalamic region forms the so-called 

 o-ptic nerves (2nd cranial). An upward protrusion forms the pineal gland 

 which is reallv a degenerated eye ; a downward protrusion forms the 

 pituitary gland the use of which is unknown (Fig. 61). The so-called 

 olfactory nerves (ist cranial) are often described as entering the forebrain; 

 they are mo.st likelv protrusions from this region. The thalamus contains 

 centres for guiding body movements by vision. 



The forebrain, brain proper or cerebrum consists of two highly con- 

 voluted expansions or hemispheres. As the grev matter is external to the 

 white matter the area of grey matter is increased the greater the 

 intricacy of convolution. The cerebrum has been described as the organ 

 of consciousness and of intelligence. From the physiological standpoint 



