98 



GENERAL CONCEPTS 



Longitudinal muscle.s 



Win^s dowrn- /Slj||jl\ Win^S up- 

 Tarrium / \ Terbam 



lin^TerOo- ^''^, 



Sternum. 



Lon_gitudinal Tardura 



muscle 



Ant. 



sternal * 

 muscles 



TcrOo- sternal muscle. 



Post. 



Ant 



Post. 



U) 



^^1 Londitudinal sections 



Figure 5.8. Diagram of the arrangement of the wing muscles of an insect. 



body, but raises the wings, which are on the opposite side of the ful- 

 crum. Then the contraction of muscles arranged longitudinally, like the 

 string of a bow, causes the tergum to bulge upward and the wing is 

 pulled do^vn for the power stroke. The mo\'ements of the body w^all are 

 barely perceptible, but, because the length of the lever on the two sides 

 of the fulcrum is so different, the distance moved by the tips of the wings 

 is several hundred times as great. 



31. Motion 



One of the fundamental properties of all kinds of protoplasm is the 

 ability to contract, a process which involves the transformation of 

 chemical energy into mechanical energy. The chemical energy of the 

 energy-rich phosphate bonds synthesized in glycolysis and in biologic 

 oxidation (p. 73) is converted into the mechanical energy of con- 

 tractile protein molecules such as actomyosin. There is reason to be- 

 lieve that the basic process for the conversion of chemical to mechan- 

 ical energy is fundamentally similar in all protoplasm, though the 

 nature of the contracting protein molecule may differ somewhat. The 

 mechanical behavior of a contracting muscle and the energy used can 

 be measured and compared with the chemical, electrical and thermal 

 changes coincident with contraction to try to understand the nature of 

 the contractile mechanism. 



Ameboid motion is the irregular flowing of protoplasm seen in 

 amebas, in the amebocytes of sponges, in the white blood cells of verte- 

 brates and in the general process of protoplasmic motion which occurs 

 during cell division. Careful microscopic study of a moving ameba re- 

 veals that not all of the protoplasm streams simultaneously. There is a 

 solid, nonmoving layer at the surface of the cell which surrounds a core 

 of liquid, flowing protoplasm. At the rear of the moving ameba, pro- 



