132 OF THE STRUCTURAL ELEMENTS OF THE HUMAN BODY. 



upon the development of the muscular substance of the uterus, which is going 

 on during the whole period of gestation, as in reality consisting in the accumu- 

 lation of a vast reservoir of cell-force, which is to be consumed in one powerful 

 effort. The contraction of the muscles ordinarily termed "voluntary," which 

 also will be shown hereafter to be dependent upon changes of form taking place 

 in the cells of their component fibrillae, is not of the " spontaneous/' but of the 

 " excited" kind; but here, too, we have evidence that the mechanical movement 

 is to be regarded but as an expression of vital force, in the fact (now universally 

 admitted by Physiologists) that every act of muscular exertion necessarily in- 

 volves as its condition the disintegration of a certain amount of muscular tissue, 

 whose components are then removed as effete by the excretory processes ; t so 

 that we may look upon the death of such cells, whose term of life might other- 

 wise have been considerably prolonged, as the result of the expenditure of their 

 peculiar modification of force, under the guise of mechanical power. 



111. What has been said of the cells which possess the attribute of motility^ 

 is also true of that still more remarkable order of cells, peculiar to the Animal 

 kingdom, by whose agency Nerve-force is developed. The nature of this force, 

 and its relations to Electricity and other physical agencies, will be discussed 

 hereafter (CHAP. v. SECT. 7); but at present it will be sufficient to state, that 

 there can be no reasonable doubt of the dependence of its production, in the 

 central organs, upon the development of the peculiar cells which constitute their 

 ganglionic or vesicular substance ; and that the progress of physiological inquiry 

 seems to justify the belief (long since entertained and expressed by the Author), 

 that cells or cell-nuclei are usually the agents in the origination of nerve-force 

 at the peripheral extremities of the nerve-fibres. This nerve-force may be re- 

 garded as the very highest manifestation of Vital Power, in virtue alike of its 

 intimate relation with Mental agency, which it serves to excite, and by which it 

 is in turn excited (CHAP, xiv.), of its power of exciting or checking Muscular 

 movements, and of the control it exerts over the Vital operations of cells in 

 general, whether these take the form of multiplication or of chemico-vital trans- 

 formation, or present themselves under any other aspect. For, so obvious is the 

 controlling and regulating action of the Nervous System, where (as in Man), it 

 attains its highest development, over those acts of nutrition, secretion, &c., 

 which essentially consist in the production and growth of cells, that many 

 Physiologists have regarded these actions as necessarily dependent upon the 

 exercise of nervous power. For this assumption, however, there is no evidence 

 whatever; and it is strongly opposed by the fact, that these actions are per- 

 formed under conditions essentially the same as they are in the Vegetable king- 

 dom, in which nervous power has no existence. And all the phenomena which 

 have been adduced in its support, are fully capable of being scientifically ex- 

 pressed by the view here advocated; for just as Electricity developed by chemi- 

 cal change may operate (by its correlation with chemical affinity) in producing 

 other chemical changes elsewhere, so may Nerve-force, which has its origin in 

 cell-formation, excite or modify the process of cell-formation in other parts, and 

 thus influence all the vital manifestations of the several tissues, whatever may 

 be their own individual characters. Further, we have evidence in the phe- 

 nomena of Nervous action (CHAP. v. SECT. 7), that the production of Nerve- 

 force, like the development of Muscular power, involves the degeneration and 

 death of a certain amount of the tissue which serves as its instrument ; so that 

 we are furnished by this fact with an additional reason for the belief, that nerv- 

 ous agencv is to be regarded as but a peculiar modus operandi of the same force 

 as that which is elsewhere operative in cell-development. 



112. Thus, then, we have distinguished the following as the principal mani- 

 festations of Cell-Life : 



