PEOTOPLASM 3 



carbon, oxygen, hydrogen, nitrogen, and small quantities of sulphur, 

 phosphorus, calcium, sodium, chlorin, magnesium, potassium and iron. 

 The principal compounds of protoplasm are proteins, which furnish 

 the main source of energy expended in function; carbohydrates; fats; 

 and water, which constitutes about three-quarters of its weight. It is 

 believed by one school of biologists (mechanists) that if we had the 



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c.tf 



FIG. 2. AMEBA PROTEUS IN MOTION. 



c.v., contractile vacuole;/.^., food vacuole; n., nucleus; w.v., water vacuoles. The 

 arrows indicate the direction of the protoplasmic flow. Note the peripheral non- 

 granular ectoplasm, and the granular endoplasm. (From Calkins' "Biology," 

 H. Holt & Co., after Sedgwick and Wilson.) 



formula for the proper stereo-isomeric association of the elements and 

 compounds of protoplasm, life could be artificially produced; another 

 school of biologists (vitalists) assume an additional 'vital principle' as 

 a prerequisite for life. 



Physical Constitution. Physically, protoplasm is a granular semi- 

 fluid or gelatinous substance. It possesses properties characteristic of 

 both solids and liquids. It is an aggregate of colloids and crystalloids. 

 The physicochemical laws which govern the crystalloids and colloids 

 underlie the properties of living matter. An organism is essentially 



