p 



ex 



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TERMINATION OF MOTOR NERVES IN VERTEBRATA. 221 



becomes more clearly defined, without undergoing any essential 

 change of form. But since portions of muscle thus excised 

 rarely die in the condition of physiological rest, but become 

 tetanically contracted before the occurrence of rigor mortis, and 

 are then fixed in this condition by coagulation, it is compara- 

 tively rare to meet with the earliest stage in which the image 

 is best shown. It is advantageous, therefore, to permit the 

 muscles to die out in the dead body, and to examine them before 

 they are so much stiffened as to become cloudy and opaque 

 It appears, therefore, that the most distinct definition of the 

 plates occurs previously to the death of the muscle, and especially 

 at the time of the death of the nerve in the stage known to 

 physiologists as that in which the muscle can no longer be 

 excited to contract through the nerves, but is still capable of 



sponding to direct stimulation. This condition, in which the 

 muscle long retains its irritability, may, as is well known, be in- 

 duced by poisoning with woorara, if the poison be given in 

 large quantities, and be allowed to act for a sufficiently long 

 period to produce evident paralysis of the terminal extremities 

 of the motor nerves. Muscles that have thus been poisoned 

 present in a distinctly marked manner an increased sharpness of 

 contour of the terminal nerve plate an appearance which may 

 consequently be regarded as the outward and visible sign o 

 commencing paralysis. This may perhaps be the result of a 

 slight contraction of the plate, or of an inappreciable retraction 

 of the granulated basis from the borders of the plate, which is 

 nevertheless sufficient to induce the alteration in the image 

 that we observe. 



In the perfectly stiffened muscle, when its reaction has be- 

 come acid, the contours of the plates change their form ; the 

 terminal nerve organ becoming continuously more and more 

 folded and notched, and at length divided off into spherical 

 masses, vesicles, or other forms, which are sometimes most re- 

 markable. The whole of these changes may also be quickly 

 induced by the action of very dilute acids ; so that, in point 

 of fact, no difference is observable from the ordinary cadaveric 

 appearances, especially if, in order to dilute the acids, serum 

 instead of water be employed, which prevents imbibition from 

 taking place. This is, perhaps, a proof that the later cadaveric 



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