280 SPECIAL PHYSIOLOGY. 



parts, are often so immediately fatal, owing to its being the centre 

 for the regulation of the respiratory movements, that time is not 

 allowed for the development of the effects, as regards the voluntary 

 movements. Thus, when one hemisphere of the brain is removed in 

 an animal, there is a diminution of power on the opposite side ; and 

 when the peduncle of one hemisphere is removed, there is a total loss 

 of voluntary power on the opposite side of the body ; so, again, effu- 

 sion of blood into, or softening of, the substance of one peduncle, or 

 of the parts above it, in man, is followed by paralysis of motion, with 

 or without paralysis of sensation on the opposite side ; whereas paraly- 

 sis of those muscles, the nerves of which proceed directly from the pons 

 or peduncles of the cerebrum, that is, from above the place of decus- 

 sation of the motor columns in the medulla oblongata, is on the same 

 side as the injury or disease ; for example, cases of extravasation of 

 blood into the left corpus striatum, or left hemisphere of the brain, 

 exhibit, during life, paralysis of the right limbs, but usually of the 

 muscles of the left side of the face ; there may sometimes be paralysis 

 of the opposite side of the face also, the reason of which is not known. 

 Decussation of the paths of the voluntary motorial stimulus in the 

 medulla oblongata is thus abundantly proved. 



Many reflex functions are performed by the medulla oblongata, in 

 common with the spinal cord. The afferent nerves connected with it, 

 supply all the important surfaces and organs at the upper part of the 

 body; viz., the skin of the face, the mucous membranes lining all its 

 cavities, the parts of the organs of the senses endowed with common 

 sensibility, and the lining membrane of the pharynx, larynx, windpipe, 

 and bronchial tubes ; lastly, they give branches to the heart and lungs, 

 as well as to the oesophagus and even the stomach. These fibres, ac- 

 cordingly, bring the effects of excitant stimuli, from all those surfaces 

 and parts, to the great and important reflex centre, formed by the 

 gray matter of the medulla oblongata, from which the effects are re- 

 flected, along certain special efferent motor fibres, on to various mus- 

 cles, which, then contracting, cause reflex movements of a most exten- 

 sive, definite, and important kind. 



Some of these movements assist in the performance of the functions 

 of special sense, as e. (/., the movements of the pupil. Others are 

 conservative or protective, in regard to the sensory organs : for ex- 

 ample, the closure of the eyelids is a reflex act ; it can even be excited 

 in animals in which the functions of the brain have been entirely sus- 

 pended or destroyed, by irritating the margins of the lids by a feather. 

 Other reflex movements protect the respiratory apparatus ; and some 

 are absolutely essential to life, as is the case with the movements of 

 deglutition, and especially with those of respiration ; for such move- 

 ments as the acts of sneezing and coughing, part of the act of swal- 

 lowing, and all the respiratory movements, are of an involuntary reflex 

 nature. They are all performed under the influence of the medulla 

 oblongata, the injury or destruction of which, impairs or arrests them. 



In reference to the respiratory functions and movements, this influ- 

 ence has been specially demonstrated by experiments on animals, 

 which have yielded both negative and positive results. Thus, even in 



