38 PROFESSOR C. R. MARSHALL ON THE 



paralysis. If not, the period of paralysis is longer than before the vagi were severed 

 and the period of recovery of the respiration is prolonged. Decerebrate animals in 

 which the section was made above the anterior quadrate bodies also proved more 

 sensitive to the paralysing action of tetra-methyl-ammonium chloride after the vagi 

 were cut than before. When the section through the mid-brain was made behind these 

 bodies, division of the vagi was followed by irregular, spasmodic, and inefficient 

 breathing, which gradually failed. All that could be deduced from the injections of 

 tetra-methyl-ammonium chloride in these vagotomised animals was that they produced 

 no stimulation of the respiration. This apparently increased sensitiveness of vago- 

 tomised animals to the influence of tetra-methyl-ammonium chloride is doubtless due 

 to the fact that after division of the vagi the centripetal impulses produced by 

 inspiration and expiration, which normally play an important part in the regulation of 

 the respiration, are cut off, and the respiratory centre is thus deprived of one of its 

 most efficient forms of stimulation to activity. After doses of atropine sufficient to 

 paralyse the pulmonary vagus, no increased sensitiveness to tetra-methyl-ammonium 

 chloride was observed, which is probably due, as some of my experiments seem to 

 suggest, to a limited antagonism existing between these substances. 



The experiments which have been described prove that the action of tetra-methyl- 

 ammonium chloride in paralysing the respiration is fundamentally due to a depressant 

 action on the myo-neural junctions of the respiratory muscles. It will be shown in 

 subsequent communications that the paralysing effect on the respiration of other tetra- 

 alkyl-ammonium compounds is proportional to their power of causing muscular paresis. 



Effect on the Circulation. 



In anaesthetised animals the intravenous injection of tetra-methyl-ammonium 

 chloride invariably causes a fall of blood-pressure and almost invariably a decided 

 diminution in the frequency of the heart-beats (fig. 6). The fall of blood-pressure, 

 occasionally after an insignificant rise, begins a few seconds after the commencement of 

 the injection and usually about two seconds before the respiration is influenced. At 

 first it is generally rapid, and later more gradual. After a dose of 1 mg. the fall may 

 occupy twenty seconds and the blood-pressure may then be less than half its original 

 height. If the respiration is inefficient, a slight asphyxial rise may occur, but commonly 

 this is absent and the low blood-pressure continues, notwithstanding an efficient 

 respiration, for one to three minutes and then gradually returns to normal. In a few 

 cases after the administration of this dose the blood-pressure has fallen to a low level 

 and no recovery has occurred. 



The fall in the frequency of the heart-beats runs a similar course, but is of 

 somewhat shorter duration. It commences with the fall of blood-pressure and may 

 amount to '25 per cent., but is generally less than this. It begins to pass away before 

 the blood-pressure commences to rise, and has usually completely passed away before 

 the blood-pressure has reached its normal height. It is apparently wholly due to 



