22 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



5. Muscular Movement. With a small blunt instrument scrape off 

 the wing muscles of a beetle (hydrophilus) and place them upon a slide 

 for microscopic study. Observe the waves of contraction passing over 

 the individual muscle-fibers. Note the increase in the diameter of the 

 fiber at the point of contraction. 



6. Stimuli. Muscle-nerve Preparation. Living substance possesses 

 the properties of irritability, conductivity, and contractility, i. e., it is 

 capable of receiving a stimulus, of conducting it to some other part 

 of its substance, and of reacting toward it in accordance with its struc- 

 tural peculiarities. A stimulus is any extraordinary change in the 



Tib. ant. long. 



Sartorius 



Add. magn. 

 Gracilis 



Tendo A chilli i 



FIG. 1. MUSCLES OF HIND LEG OF FROG. (Ecker.) 



environment of the living entity, in consequence of which it evolves 

 some form of energy. In this way a muscle may be made to contract 

 and a gland to secrete. As a matter of convenience we usually employ 

 the former tissue and principally that derived from the frog. 



Grasp the pelvis of a lightly etherized frog between the thumb and 

 index-finger of your left hand, allowing the ventral aspect of the thorax 

 and head to rest upon your third and fourth fingers. With your right 

 hand move the point of a small scalpel rapidly backward from between 

 the eyes until you feel a depression at the junction of the head with the 

 spinal column. This depression lies at the atlo-axoid articulation. 



