THE MECHANISM OF LIFE 



585 



of centrifugal nerves those of the motor nerves in cross-striated 

 muscles are most characteristic. Here the transition of the nerve- 

 hbre into the muscle-substance is mediated by a specially differ- 

 entiated end-organ, the motor end-plate, a flat or branched extension 

 ol the axis-cylinder in the sarcoplasm. The latter, which in this 

 place IS very granular and is characterised by many nuclei, is 

 covered by the sarcolemma of the muscle-fibre : the sarcolemma 

 here passes over directly into the neurilemma of the nerve (Fig. 

 !l "^' ^^^ manner of ending of the centrifugal nerves in 

 other organs, such as smooth muscle-cells, gland-cells, photo- 



Pig. 285.— Nerre-ondings. /, Olfactory cells ; A, from the frog, B.from man. The slender, spindle- 

 shaped cells are the olfactory cells ; to these the nerve goes ; the broad cells, branched below 

 .ire epithelial supporting-cells. (After Frey.) //, Nerve end-plate from the conjunctiva of a 

 calf. (After SchiefEerdecker.) ///, Motor end-plate in cross-striated muscle, seen from the side. 

 (From Lang.) 



genie cells, etc., appears to be much less complicated ; but these 

 relations need more careful investigation. 



Only through the central control of all functions of the whole 

 organism by the nervous system is it possible for the cell- 

 community of the animal body to be differentiated so extensively 

 as it is. Only when at the proper moment this or that organ is 

 put into activity or remains at rest, only when this or that organ 

 reacts appropriately to an influence in this or that part of the 

 body, only when the cells, tissues and organs work together in the 

 most perfect harmony, can so complicated a mecha.nism be 

 developed, as exists in the cell-community of the vertebrates and 

 especially of man. 



