478 ON THE PHYSIOLOGICAL ACTION OF XITRO- GLYCERINE. 



which have been found to be mnscle-poisons in an unpublished 

 research on which one of us (Brunton) in conjunction with Mr 

 Gresswell is at present engaged in this laboratory. 



Action on Motor JVerves. — On ligaturing the vessels in one lec!, 

 of a frog so as to prevent the circulation of poisoned blood in 

 that limb, the nerve being left uninjured, we. have found that 

 when paralysis had begun to appear, the spasms which could 

 be observed were slightly more marked in the ligatured limb. 

 On testing the irritability of the motor nerves after deatli, they 

 were found to respond much more readily to an induced current 

 in the ligatured than in the non -ligatured leg ; but as tlie 

 muscles of the non-ligatured leg responded but feebly to a 

 current directly applied to them, we are at present unable to 

 say whether the paralysis is entirely due to the action of the 

 •poison on the muscles, or whether it affects the motor nerves as 

 well. We may possibly be able to decide this point by making 

 farther experiments, similar to those which we have already 

 performed, but in winter, when the muscles preserve their irrit- 

 ability longer than in summer, during which our experiments 

 were made. We also propose to try them with Bana escuhnta 

 instead of Rana temjooraria, the muscles of these tw^o species of 

 frog having been shown by Schmiedeberg to be very differently 

 affected by caffein, a poison having an action similar in some 

 respects to that of nitro-glycerine. 



Action on the Spinal Cord. — The loss of reflex action both in 

 frogs and cats, in the advanced stages of poisoning, indicates 

 that the cord is paralysed ; and the persistence of reflex action 

 in. parts supplied by cranial nerves, such as the eye and. ear, 

 after it has disappeared from other parts of the body, indi- 

 cates that the cord is paralysed before the ganglia at the base 

 of the brain. 



Action on the Brain. — One of the most remarkable effects of 

 nitro-glycerine is the intense headache it produces, even in 

 infinitesimal doses. Almost all observers agree about the 

 fact of its producing headache, but they differ regarding the 

 nature of the headache. According to our experience, it is not 

 always of the same kind, being sometimes frontal, sometimes 

 occipital, sometimes affecting one side only, and at other times 



