N. MATERIA MEDICA, THERAPEUTICS, AND HYGIENE.559 



people, and why it becomes subsequently rarer or less danger- 

 ous, as has frequently been observed. 



After the lapse of several generations, however, a popula- 

 tion moderately affected by a disease approaches the condi- 

 tion of one which has never had it, and an increased intensity 

 may then ensue. Applying these principles to the small- 

 pox, M.De Candolle suggests that, at the epoch when Jenner 

 introduced vaccination, the variolic affection had become en- 

 feebled in proportion to the anterior epochs. The vaccina- 

 tion was then more efficacious as applied at this particular 

 period. Small-pox having almost disappeared from Europe 

 for two generations, a new population has sprung up less ac- 

 customed to it, and this cause of recrudescence tends now 

 to render vaccination less potent. The author does not pre- 

 tend that this is the only cause, but that, in connection with 

 others, it exists, and in such a manner as to produce the re- 

 sults specified. Mem. iSoc. Physique de Geneve, XXL, 1870, 

 351. 



ACTION OF STRYCHNINE ON VASO-MOTOR NERVES. 



Dr. Sigmund Meyer has published the results of some ex- 

 periments upon the action of strychnine on the vaso-motor 

 nerve-centre, using for the purpose dogs and rabbits, and call- 

 ing to his help the cymograph. In most of the experiments 

 the poison was introduced into the venous circulation in the 

 form of an aqueous solution of nitrite of strychnine. In a 

 short time after the injection a very considerable increase of 

 the pressure of arterial blood was appreciable. The decided 

 increase of pressure in the aortic system occurred in animals 

 breathing independently, as well as those poisoned with cu- 

 rare, in which artificial respiration had been produced. In 

 the course of the experiment, it was shown that the increase 

 of pressure described is caused by a contraction of the smaller 

 arteries consequent upon a central excitation of the vaso- 

 motor centre in the brain, and the increased elevation of the 

 resistance to the current of the blood in the arterial system. 

 The contraction of the arteries in question could easily be 

 appreciated by direct inspection of the intestines. While the 

 pressure of the blood was very high, the occurrence of the 

 periodic variation discovered by Troube was frequently ob- 

 served. 1 8 C, December 1 3, 1 871 , 790. 



