282 PROFESSOR C. R. MARSHALL ON 



paralysed ; it began to get shallower ten seconds after the commencement of the 

 injection, and reached its lowest point five seconds later, from which time it very 

 gradually returned to the normal. The blood-pressure commenced to fall before the 

 respiration was affected, and fell from 87 mm. before the injection to 58 mm. twelve 

 seconds after the commencement of the injection. From this point it gradually rose in 

 three minutes to 107 mm. The effect of a subsequent injection of 0"02 g. caused 

 almost complete cessation of respiration for half a minute, and then a very gradual 

 return to normal breathing. The fall in the respiratory curve, however, was less 

 abrupt, the blood-pressure was more quickly and more powerfully influenced, and the 

 return of normal respiration was later than occurs after protocatechyl-tropeine. 



The other synthetic tropeines I have investigated do not distinctly influence the 

 respiration in doses which depress the vagal endings, but doses of both atropine and 

 homatropine may be found which will cause temporary cessation of the respiration. 

 The dose of atropine necessary for rabbits is about O'OOOl g. per kg. body-weight 

 intravenously. After this dose, however, the return of normal respiration is less 

 rapid than after the administration of protocatechyl-tropeine. Homatropine, in doses 

 of 0'005 g. per kg. body-weight intravenously, produces a more transient effect on the 

 respiration and a greater effect on the blood -pressure than atropine in the dose 

 mentioned. I have also succeeded in producing temporary stoppage of the respiration 

 with the allied alkaloid cocaine, and with /3-eucaine and other local anaesthetics. I 

 failed, however, to produce the effect with ammonium hydroxide. A certain degree of 

 recovery may, with appropriate doses, be obtained after intravenous administration of 

 this substance, but this recovery is not maintained, and the respiration fails again unless 

 artificial respiration is performed. The best effect I have obtained was from the 

 injection of 0*025 g. ammonium hydroxide per kilogramme body-weight. Larger 

 amounts of ammonium hydroxide may be followed by a few spontaneous respirations, 

 but they paralyse the respiration permanently unless it is restored by artificial means. 

 Doses less than O'Ol g. per kilogramme generally increase the respiratory movements; 

 above this dose the movements are diminished. 



Comparison op Effects on Blood-Pressure. 



All the drugs previously mentioned, in doses which temporarily abolish the respira- 

 tion, diminish in rabbits the frequency of the heart-beats. The effect is greatest in 

 the case of methyl-phenyl-isoxazol-metbochloride and tetramethyl-ammonium chloride, 

 and least in that of the tropeines. In most cases there is also a fall in blood-pressure. 

 Methyl-phenyl-isoxazol-methochloride, however, notwithstanding the marked slowing of 

 the heart produced by it, causes, after a preliminary slight fall, a rise of blood-pressure, 

 which is due, according to Tappeiner,* to stimulation of the medullary centres. The 

 slowing of the heart and fall of blood-pressure produced by tetramethyl-ammonium 



* hoc. cit. 



