XXIX.] PITHING — CILIARY MOTION, ETC. 177 



blade, else two large blood-vessels will be injured. The operation 

 bhould be performed witly)ut losing any blood. 



2. Ciliary Motion. 



{a.) Destroy the brain and spinal cord of a frog. Place the 

 frog on its back on a frog-plate covered with cork well- waxed or 

 coated with paraffin. Divide the lower jaw longitudinally, and 

 carry the incision backwards through the pharynx and oesophagus. 

 Pin back the flaps. Moisten the mucous membrane, if necessary, 

 with normal saline. 



(b.) Make a small cork flag, and rest it on the mucous mem- 

 brane covering the hard palate between the eyes. It will be 

 rapidly carried backwards by ciliary motion towards the stomach. 

 Repeat the experiment, and determine the time the flag takes to 

 travel a given distance. 



(c.) Apply heat to the preparation, and observe that the cork 

 travels much faster. 



{(l.) Grains of charcoal or Berlin blue are carried backwards in a similar 

 manner, 



{e.) With a hot wire cauterise superficially a small area of the mucous 

 membrane in a preparation bestrewn with grains of charcoal. The ciliary 

 movement stops not only at the cauterised area, but also in a triangular 

 area whose apex is at the burned point, and whose base is directed towards 

 the oesophagus. It would seem, therefore, that the movements of the cilia 

 in individual cells are not independent of the movements in neighbouring 

 cells. 



3. Anatomy of the Nerve-Muscle Preparation.— Before mak- 

 ing this preparation, the student must familiarise himself with 

 the anatomy of the hind limb of the frog. On a dead frog study 

 the arrangement of the muscles, as shown in fig. 105. The skin of 

 the frog is removed, the frog placed on its belly, and the muscles 

 viewed from behind. On the outside of the thigh, the triceps 

 fenwris (tr), composed of the rect/is anterior (ra), the vastus 

 externns (ve), and the vafitus internus, not seen from behind. On 

 the median side, the semi-memhranosus (.sw), and between the two 

 the small narrow biceps (b). The biceps is readily observed, at 

 the lateral margin of the large semi-membranosus, by its shining 

 tendon in the middle of the lower half of the thigh. Notice, also, 

 the coccygeo-iliacus (ci), the (jluteus (gl), the i»jri/ormis (7;), and 

 tlie rectus internns minor (ri). In the leg, the (jaslrorwmias (r/), 

 with its tendo Achillis, the tibialis anticus (ta), and the peroneus 

 (pe). 



4. Make a Dissection. 



(a.) Remove the skin from the leg of a dead frog ; with a blunt 

 needle, called a " seeker " or a '' finder," or a glass rod drawn out to 



M 



