GENERAL FUNCTIONS OF NERVOUS SYSTEM. 475 



sex, and of the ova containing germ-cells in the other, the subsequent 

 fertilization of the latter by the former, and the changes consequent 

 upon that act, together making up the function of Generation, may be 

 all regarded as modifications of the ordinary Nutritive processes ; and 

 are effected, like these, by the inherent powers of the parts concerned 

 in them, at the expense of the materials supplied by the blood, without 

 any direct dependence upon the Nervous system. 



841. Still, although the various processes, which make up the essen- 

 tial part of the nutritive operations, in Animals as in Plants, are no 

 more dependent on any peculiar influence derived from a Nervous sys- 

 tem, in the former, than they are in the latter, it must be evident, from 

 the details already given, that there must be in Animals various acces- 

 sory changes, which are requisite for the continuance of the former, and 

 which can only be effected by the peculiar powers with which Animals 

 are endowed. Thus, to commence with Digestion ; this preliminary 

 process, which the nature of the food of the plant renders unnecessary 

 for -its maintenance, can only be accomplished by the introduction of the 

 food into a cavity or sac, in which it may be submitted to the action of 

 the solvent fluid. The operation of grasping arid swallowing the food, 

 wherever it is performed, is accomplished through the agency of the 

 Nervous system ; and if it be checked by the loss of Nervous power, the 

 Digestive process must cease for want of material. So, again, although 

 interchange of gaseous ingredients between the atmosphere and the 

 circulating fluid may take place with sufficient energy in Plants and the 

 lower Animals, through the mere exposure of the general surface to the 

 atmosphere, yet we find that, in all the higher Animals, certain move- 

 ments are requisite, for the continual renewal of the air or water which 

 are in contact with one side of the respiratory surface, and of the blood 

 which is in relation with the other : for the direction of which move- 

 ments a Nervous system is requisite. In the excretory processes, 

 moreover, the removal of the effete matters from the body can only be 

 accomplished, in the higher Animals, by certain combined movements ; 

 the object of which is, to take up the products that are separated by 

 the action of the proper secreting cells, and to carry them to the exterior 

 of the body, there to be set free ; and these combined movements can 

 only be effected by the agency of the Nervous system. Lastly, in the 

 act of Reproduction, the arrangement of the sexual organs in Animals 

 requires that a certain set of movements should be adapted to bring 

 together the contents of the "sperm-cells" of the male, and of the "germ- 

 cells" of the female ; and also for the expulsion of the ovum from the 

 body of the latter, in a state of more or less advanced development. 

 For these movements a special arrangement is made, in the construction 

 of the Nervous system, and in the application of its peculiar powers. 



842. Thus we see that, although the Organic functions of the Animal 

 are essentially independent of the Nervous System, this system affords 

 the conditions which are requisite for their continued maintenance ; 

 being the instrument whereby the muscles are called into action for the 

 performance of the various combined actions, that constitute the mecha- 

 nism (so to speak) by which the Vegetative part of the fabric is com- 

 bined with the Animal portion of the organism. We are not to suppose, 



