572 GENERAL PHYSIOLOGY 



cilia be cut into at one place, the two halves are able to act inde- 

 pendently of one another. 1 Even if a single cilium with a droplet 

 of attached protoplasm be cut off from the cell-body, it acts 

 rhythmically and spontaneously until it perishes. It must, there- 

 fore, be assumed that the complete dependence- of the individual 

 cilium and the individual ciliated cell upon the one next it, is 

 conditioned by some kind of mechanism in the basal protoplasm, 

 which hinders all independent movement, arid mediates only im- 

 pulses from that side. 2 But this is only possible when in the 

 ciliated epithelium an unbroken continuity of the basal protoplasm 

 exists throughout the whole row of cells. It is known that proto- 

 plasmic connections between the individual cells in the cell- 

 community are wide-spread in both plants and animals. 



Finally, the most thorough -going despotism exists in the higher 

 animal in the dominion of the nerve-cells over the cells of all kinds 

 of tissues. The higher we go in the animal series, the more we 

 see the tendency of the nerve-cells to extend their dominion to all 

 the tissues of the body. The loss of independence thus resulting 

 goes so far in many tissue-cells, that their vital activity sinks to a 

 minimum so long as it is not stimulated by impulses from the nerve- 

 cells. Spontaneity is apparently wholly lost. A skeletal muscle 

 in the vertebrates never performs a contraction spontaneously ; 

 the ganglion-cells of the central nervous system alone by their im- 

 pulses are able to put it into contraction. We ought not to be 

 misled by this lack of spontaneous contractions into believing that 

 the metabolic processes that characterise muscular activity are at 

 a complete standstill during rest. This is only apparently the case. 

 As a comparison of the arterial blood streaming to the muscle with 

 the venous blood coming from it teaches, the same metabolic pro- 

 cesses go on in the muscle during rest as during activity, but in so 

 slight extent and so uniformly that a contraction is not thus 

 brought about. But if by nervous influence they undergo a sudden 

 augmentation, the contraction appears. Wholly analogous to the 

 dependence of the muscle-cells is the relation of many other 

 tissue-cells, e.g., gland-cells, to the central nervous system ; and 

 even the relation of the ganglion-cells to one another is partly of 

 the same kind. 



The general principle upon which is based the formation of the 

 cell-community, and with it the formation of a more or less close 

 dependence of the individual cells upon one another, is the principle 

 that controls all development. It is the principle of utility. The 

 fact that the cells remain together after division and thus form a 

 community consisting of several like components, which occurs in 

 the Protista, secures the advantage of greater protection for the 

 individual cell. But, as has been seen, a certain dependence of 

 the individual cells upon one another is conditioned by this simple 



1 Of. Verworn ('89, 1). 2 C f Verworn ('90, 2). 



