FUNCTIONS OF THE MEDULLA OBLONGATA. 



727 



spiratory movements still persisting. It is a very common thing in vivisections to kill an 

 animal by breaking up the medulla. In a dog, for example, we grasp the head firmly 

 with the left hand, flex it forcibly upon the neck, and penetrate with a stylet a little behind 

 the occipital protuberance, entering between the atlas and the skull. By 

 a rapid lateral motion of the instrument, the medulla is broken up, and 

 the animal instantly ceases to breathe. There are no struggles, no mani- 

 festations of the distress of asphyxia; the respiratory muscles simply 

 cease their action, and the animal loses instantly the sense of want of 

 air. A striking contrast to this is presented when the trachea is tied or 

 when all of the respiratory muscles are paralyzed without touching the 

 medulla. 



In another chapter, we have insisted upon the mechanism of the reflex 

 phenomena of respiration. We have conclusively shown by experiments, 

 that an impression is received by the sensory nerves of the general sys- 

 tem, which is due to want of oxygen and not to the irritation produced 

 by carbonic acid ; and that this impression is conveyed to the medulla 

 oblongata and gives rise to the reflex movements of respiration. If this 

 impression be abolished, there are no respiratory movements ; and if the 

 medulla, the sole centre capable of receiving this impression and of gen- 

 erating the stimulus sent to the respiratory muscles, be destroyed, respi- 

 ration instantly ceases, without any sensation of asphyxia. 



Vital Point (so called). Since it has been definitely ascertained that 

 destruction of a restricted portion of the gray substance of the medulla 

 produces instantaneous and permanent arrest of the respiratory move- 

 ments, Flourens and others have spoken of this centre as the vital knot, 

 destruction of which is immediately followed by death. With our 

 present knowledge of the properties and functions of the different tissues 

 and organs of which the body is composed, it is almost unnecessary to 

 present any arguments to show the unphilosophical character of such a 

 sweeping proposition. We can hardly imagine such a thing as instan- 

 taneous death of the entire organism ; still less can it be assumed that 

 any restricted portion of the nervous system is the one essential, vital 

 point. Probably, a very powerful electric discharge passed through the 

 entire cerebro-spinal axis produces the nearest approach to instantaneous 

 death of any thing of which we have any knowledge ; but, even here, it FIG. 230. Stylet 

 is by no means certain that some parts do not for a time retain their so- 

 called vital properties. In apparent death, the nerves and the heart may 

 be shown to retain their characteristic properties; the muscles will con- 

 tract under stimulus, and will appropriate oxygen and give off carbonic acid, or respire ; 

 the glands may be made to secrete, etc. ; and no one can assume that, under these con- 

 ditions, the entire organism is dead. We really know of no such thing as death, except 

 as the various tissues and organs which go to make up the entire body become so altered 

 as to lose their physiological properties beyond the possibility of restoration ; and this 

 never occurs for all parts of the organism in an instant. A person drowned may be to all 

 appearances dead, and would certainly die without measures for restoration ; yet, in 

 such instances, restoration may be accomplished, the period of apparent death being 

 simply a blank, as far as the recollection of the individual is concerned. It is as utterly 

 impossible to determine the exact instant when the vital principle, or whatever it may 

 be called, leaves the body in death, as to indicate the time when the organism becomes 

 a living being. Death is nothing more than a permanent destruction of so-called vital 

 physiological properties ; and this occurs successively, and at different periods, for differ- 

 ent tissues and organs. 



for breaking up 

 flte medulla ob- 

 longata. (Ber- 

 nard.) 



