6 HAND-BOOK OF PHYSIOLOGY. 



nutrition, Beale has named it Germinal matter or Bioplasm. Of these 

 terms the one most in vogue at the present day is Protoplasm, and inas- 

 much as all life, both in the animal and vegetable kingdoms, is associated 

 with protoplasm, we are justified in describing it, with Huxley, as the 

 "physical basis of life." 



A cell may now be defined as a nucleated mass of protoplasm, 1 of 

 microscopic size, which possesses sufficient individuality to have a life- 

 history of its own. Each cell goes through the same cycle of changes 

 as the whole organism, though doubtless in a much shorter time. Begin- 

 ning with its origin from some pre-existing cell, it grows, produces other 

 cells, and finally dies. It is true that several lower forms of life consist of 

 non-nucleated protoplasm, but the above definition holds good for all 

 the higher plants and animals. 



Hence a summary of the manifestations of cell-life is really an account 

 of the vital activities of protoplasm. 



Protoplasm. Physical characters. Physically, protoplasm is viscid, 

 varying in consistency from semi-fluid to stronglyc oherent. Chemical 

 characters. Chemically, living protoplasm is an extremely unstable albu- 

 minoid substance, insoluble in water. It is neutral or weakly alkaline in 

 reaction. It undergoes heat stiffening or coagulation at about 130F. 

 (54'5C.), and hence no organism can live when its own temperature is 

 raised beyond this point, though, of course, many can exist for a time in 

 a much hotter atmosphere, since they possess the means of regulating 

 their own temperature. Besides the coagulation produced by heat, pro- 

 toplasm is coagulated by all the reagents which produce this change in 

 albumen. If not-living protoplasm be subjected to chemical analysis it 

 is found to be made up of numerous bodies 2 besides albumen, e.g., of gly- 

 cogen, lecithin, salts and water, so that if living protoplasm be, as some 

 believe, an independent chemical body, when it no longer possesses life, 

 it undergoes a disintegration which is accompanied by the appearance of 

 these new chemical substances. When it is examined under the micro- 

 scope two varieties of protoplasm are recognized the hyaline, and the 

 granular. Both are alike transparent, but the former is perfectly homo- 

 geneous, while the latter (the more common variety) contains small gran- 

 ules or molecules of various sizes and shapes. Globules of watery fluid 

 are also sometimes found in protoplasm; they look like clear spaces in it, 

 and are hence called vacuoles. 



Vital or Physiological characters. These may be conveniently treated 

 under the three heads of I. Motion; II. Nutrition; and III. Repro- 

 duction. 



1 In the Luman body the cells range from the red blood-cell (-g^Vo" in.) to the gang- 

 lion-cell (y^-) in. 



2 For an account of which, reference should be made to the Appendix. 



