22 



EXPERIMENTAL PHYSIOLOGY 



tion consisting of the knee-joint with portions of the femur and tibia, the gastro- 

 cnemius muscle, and the sciatic nerve ; this is termed a muacle-nerve preparation. 

 For many experiments a longer nerve is needed. To obtain this the sciatic 

 nerve is to be exposed as before from behind, but not tied or cut; it should 

 indeed not be touched in its course by any instrument. Then seize the 

 urostyle with forceps, and cut it and the muscles attached to it entirely away 

 with scissors. The nerves previously seen behind the kidneys are now exposed 

 from the back ; they are continuous on each side with the corresponding sciatic 

 nerve. To isolate the nerve along its whole length, sever the attachment of 

 the ilium to the sacrum. Split the end of the spinal column longitudinally with 

 scissors, and, holding one-half with forceps, lift it up obliquely, but not at too 



mac. 



Tensor fasc lat. 



Triceps femoris (cruralis). 

 Add. magn. 



Ext. crur. brev. 



Tibialis ant. long. 



Tibialis ant. brev 



Tars, ant 



Gastrocnemios . 

 Tibialis posticus. 



Int. iliac. 

 Add. long. 

 Sartorius. 



Pectineus. 

 Eect. abd. 

 Add. magn. 

 Gracilis major. 



Gracilis minor. 



Crural bone (tibia and fibula). 



Tendo AchUlis. 



FIG. 29. MUSCLES OF FROG-LEG : VENTRAL ASPECT (GAUPP). 



sharp an angle, along with the nerves issuing from it to form the sciatic. 

 Gradually dissect out the nerve from above down as before described, snipping 

 the lateral branches with scissors (without touching the main nerve) until the 

 back of the knee is reached. Lay the long piece of nerve thus isolated upon the 

 gastrocnemius muscle, and, as before, cut through the middle of the femur after 

 clearing the attachments of the thigh-muscles away from its lower end ; you 

 now have a nerve-muscle preparation with long nerve. Place a piece of paper 

 impregnated with paraffin on the frog-cork, and lay the nerve out clear of the 

 muscle, fixing a pair of electrodes so that the nerve lies across them. Keep 

 both muscle and nerve but especially the latter wet with normal salt solution 

 or Ringer's solution. 



With a nerve-muscle preparation thus obtained perform the 

 following experiments, which are, for the most part, similar to those 

 already performed upon the tongue. Note down all your results. 



