12 INTRODUCTION TO CYTOLOGY 



early workers had focussed their attention, turned out to be of secondary 

 importance. The cell was thus seen to be primarily the organized 

 protoplasmic mass, to which Hanstein in 1880 applied the convenient 

 term protoplast. 



Extensive studies on the physical nature of protoplasm were soon 

 undertaken by Kiihne (1864), Cienkowski (1863), and de Bary (1859, 

 L864); and there later followed the well-known structural theories of 

 Klein, Flemming, Altman, and Btitschli. (See Chapter III.) 



Yon Mohl as early as 1837 held that the plastid is a protoplasmic 

 bod}-. The classic researches of Nageli (1858, 1863) on plastids and 

 starch grains laid the foundation for our knowledge of these bodies, which 

 was greatly extended in later years by Meyer (1881, 1883, etc.) and 

 Schimper (1880, etc.). (See Chapter VI.) 



It would be difficult to overestimate the value, both practical and 

 theoretical, of the Protoplasm Doctrine, for its establishment has not 

 only led to knowledge by which the conditions of life have been materially 

 improved, but has also been an important factor in assisting man to a 

 modern, rational outlook on organic nature, in which he has learned to 

 include himself. It is not too much to say that the identification of 

 protoplasm as the material substratum of the life processes was one of 

 the most significant events of the nineteenth century. The doctrine 

 was furnished with a popular expression by Huxley in his well-known 

 essay, The Physical Basis of Life (1868). 



The New Conception of the Cell. — The conception of the cell had now 

 developed into something quite different from what it had been in the 

 minds of the founders of the Cell Theory. The cell was now recognized 

 as a protoplasmic unit, and the ideas of these men concerning the origin 

 and multiplication of cells had been overthrown. Future researches 

 were to show more clearly the importance of the cell in connection with 

 development and inheritance, and certain limits were to be set to the 

 conception of the cell as a unit of function and organization. To Schlei- 

 den and Schwann the multicellular plant or animal appeared as little 

 more than a cell aggregate, the cells being the primary individualities; 

 the organism was looked upon as something completely dependent upon 

 their varied activities for all its phenomena. "The cause of nutrition 

 and growth," said Schwann, " resides not in the organism as a whole, 

 but in the separate elementary parts — the cells." This elementalistic 

 conception of the organism as an aggregate of independent vital units 

 governing the activities of the whole dominated biology for many years, 

 notwithstanding its severe criticism by Sachs, de Bary, and many other 

 later writers who pointed out that, owing to the high degree of physio- 

 logical differentiation among the various tissues and organs, the cell 

 cannot be regarded merely as an independent unit, but as an integral 

 part of a higher individual organization, and that as such the exercise 



