BY DR. MICHAEL FOSTER. 399 



no escape of the current into the surrounding muscles. This 

 may be effected by slipping under the electrodes a small piece 

 of India-rubber sheeting. 



If the animal 1ms been thoroughly poisoned, no contractions 

 whatever in the muscles of the leg will follow upon the appli- 

 cation of a stimulus, however strong, to the nerve. If con- 

 tractions do make their appearance, the poisoning is not com- 

 plete ; and the student must wait or inject a further quantity 

 of the poison. 



The nerve having been proved to be insensible to stimuli, 

 lay bare any of the muscles of the leg and apply the electrodes 

 directly to them. Contractions will be manifest upon the ap- 

 plication of a very slight stimulus. 



The effect of urari is to destroy (or suspend) the irritability 

 of nerves but not that of muscles. 



Obs. II. In a strong frog make an incision through the skin 

 between the ilium and coccyx along the line k, m, fig- 266 

 Cut cautiously through the ileo-coccygeal muscle (fig. 267 d) 

 until the peritoneal cavity is reached. The three nerves (fig. 



)5, 7' 8' 9'), which go to form the sciatic nerve, will come into 

 when the sides of the wound are held apart. Very cau- 



>usly, by means of a small aneurism needle, pass a thread 



ider these nerves, putting it under from the outside and 



inging it out again on the median side. Be very careful not 

 1o wound the bloodvessels. 



Rolpt the same process on the other side, passing the same 

 thread under the nerves of that side too, but putting it in at 

 the median side and bringing it out at the outside. The thread 

 will now be in the position of the line o p q in fig. 2G6, with 

 the nerves of one side lying over it between o and p, and those 

 of the other side over it between p and q. Tie the thread very 

 tightly round the abdomen, so as to check entirely the flow of 

 blood to the lower limbs. All this may be done under a slight 

 dose of chloroform. The nerves thus form the only means of 

 communication between the hind limbs and the trunk, the 

 vascular communication being entirely stopped. Now inject 

 a small quantity of urari into the back, and wait until the 

 poison has had time to produce its effects in that part of the 

 body to which alone it has access, viz., the part above the liga- 

 ture. 



The following facts may then be determined : 



Though there are no voluntary movements in the body, head, 

 or fore limbs, some slight (voluntary?) movements may some- 

 times be witnessed in the hind limbs. 



Pinching, or otherwise stimulating, either hind foot may 

 produce movements in either one or both hind limbs, but in no 

 other part of the body. 



Pinching, or otherwise stimulating, the skin of the head, 



