THE CELL IN RELATION TO THE MULTICELLULAR BODY 59 



earned, it has now been clearly demonstrated that only in a limited 

 sense can the cells be regarded as cooperating units. They are 

 rather local centres of a formative power pervading the growing 

 mass as a whole, 1 and the physiological autonomy of the individual 

 cell falls into the background. It is true that the cells may acquire 

 a high degree of physiological independence in the later stages of 

 embryological development. The facts to be discussed in the eighth 

 and ninth chapters will, however, show strong reason for the conclu- 

 sion that this is a secondary result of development, through which the 

 cells become, as it were, emancipated in a greater or less degree 

 from the general control. Broadly viewed, therefore, the life of the 

 multicellular organism is to be conceived as a whole ; and the appar- 

 ently composite character which it may exhibit is owing to a second- 

 ary distribution of its energies among local centres of action. 2 



In this light the structural relations of tissue-cells become a ques- 

 tion of great interest ; for we have here to seek the means by which 

 the individual cell comes into relation with the totality of the organ- 

 ism, and by which the general equilibrium of the body is maintained. 

 It must be confessed that the results of microscopical research have 

 not thus far given a very certain answer to this question. Though 

 the tissue-cells are often apparently separated from one another by a 

 non-living intercellular substance, which may appear in the form of 

 solid walls, it is by no means certain that their organic continuity is 

 thus actually severed. Many cases are known in which division of 

 the nucleus is not followed by division of the cell-body, so that multi- 

 nuclear cells or syncytia are thus formed, consisting of a continuous 

 mass of protoplasm through which the nuclei are scattered. Heitz- 

 mann long since contended ( '73), though on insufficient evidence, that 

 division is incomplete in nearly all forms of tissue, and that even when 

 cell-walls are formed they are traversed by strands of protoplasm by 

 means of which the cell-bodies remain in organic continuity. The 

 whole body was thus conceived by him as a syncytium, the cells 

 being no more than nodal points in a general reticulum, and the body 

 forming a continuous protoplasmic mass. 



This interesting view, long received with scepticism, has been to a 

 considerable extent sustained by later researches, and though it still 

 remains sub judice, has been definitely accepted in its entirety by some 

 recent workers. The existence of protoplasmic cell-bridges between 

 the sieve-tubes of plants has long been known ; and Tangl's dis- 

 covery, in 1879, of similar connections between the endosperm-cells 

 was followed by the demonstration by Gardiner, Kienitz-Gerloff, A. 

 Meyer, and many others, that in nearly all plant-tissues the cell-walls 



1 Cf. Chapters VIII., IX. 



2 For a fuller discussion see pp. 388 and 413. 



