XXX.] NERVE-MUSCLE PREPARATION, ETC. 1 79 



pyriformis (p), and also tlie ilio-coccygoal muscle, when tlie tlirca 

 spinal nerves — the ytli, 8th, and 9th — which form the sciatic nerve, 

 come hito view. It can be seen from the abdominal side after 

 opening the belly and removing the viscera, including the kidneys. 

 On its way from the sacral plexus to the thigh, it gives off cutan- 

 eous and muscular branches for the pelvis and thigh. 



5. Double Semi-Membranosus and Gracilis [Pick's Method). — I am indebted 

 to Prof. Fick and Dr Schenk of "VVilrzburg, for showing me the method of pre- 

 paring this— one of the most convenient of preparations. 



{a.) After pithing a frog, and removing its skin to expose the muscles of the 

 hind Hmbs, remove the few fibres of the rectus internus minor which are torn 

 across when the skin is torn off. Divide the fascia at the outer margins of the 

 semi-membranosus and gracihs, until the insertion of these two muscles into 

 the knee is reached, then, with strong scissors, divide tlxe leg bone just umler 

 the knee-joint, so that the osseous insertion of both muscles is retained. 

 Divide the femur just above the knee-joint, and separate all the muscles in- 

 serted into it, save the two muscles one is isolating. Separate the two muscles 

 from the other muscles of the thigh up to the symphysis. Leave the two 

 muscles in connection with the symphysis, divide the other muscles, disar- 

 ticulate the femur at the acetabulum. In preparing the n)uscles in this way 

 the semi-tendinosus, which lies between the two on the side towards the bone, 

 is usually left. It is easy to separate it by dividing its insertion into the 

 femur, and then its two heads at the pelvis. 



[b. ) Make a similar dissection on the opposite side. Bore a hole with an awl 

 through both acetabula. Through this a hook can be placed. 



Thus we have two muscles with nearly straight fibres which can be placed 

 "side by side," thus giving a short muscle with great sectional area, or they 

 can be placed "one behind the other," a piece of bone, the symphysis inter- 

 vening, thus giving a long muscle with half the sectional area. This prepara- 

 tion is extensively used by Prof. Fick, and has many advantages. 



6. Indifferent Fluids — Normal Saline. — Dissolve 6 grams of dried sodic 

 chloride in 1000 cc. of water. This is the best fluid to use to moisten tissues 

 when a large quantity is required. For nerve the aqueous humor of the frog's 

 eye is the best. It can readily be obtained by perforating the cornea with a 

 fine glass pipette. 



LESSON XXX, 



NERVE - MUSCLE PREPARATION — STIMULATION 

 OP NERVE— MECHANICAL, CHEMICAL, AND 

 THERMAL STIMULI. 



1. Nerve-Muscle Preparation. — Apparatus. — Frog, seeker, 

 narrow-bladed scalpel, a small and a large pair of scissors, forceps, 

 towel, and a porcelain plate. 



(A.) (a.) Pith a frog, destroying the brain and spinal cord, and 

 place the frog on its belly on a frog-plate. With scissors make an 



