84 GENERAL VIEW OF THE FUNCTIONS. 



of the Nervous System have none but an indirect influence or control over 

 them. ' It is, therefore, quite philosophical to distinguish these Organic Func- 

 tions, or phenomena of Vegetative Life, from those concerned in the Life of 

 Relation, or Animal Life. The distinction is, indeed, of great practical im- 

 portance, and lies at the foundation of all Physiological Science ; yet it is seldom 

 accurately made, and a very confused notion on the subject is generally pre- 

 valent. It is commonly said, for example, that the function of Respiration is 

 the connecting link between the two : the fact being, however, that the true 

 process of Respiration is no more a function of Animal life than is any ordi- 

 nary process of secretion; but that, in order to secure that constant interchange 

 of air, which is necessary to its performance, the assistance of the nervous and 

 muscular systems is called in, though not in a manner which necessarily in- 

 volves either consciousness or will. 



98. The process of Reproduction, like that of Nutrition, has been until re- 

 cently involved in great obscurity ; and although it cannot be said to be yet 

 fully elucidated, it has been brought, by late investigations, far more within 

 our comprehension than was formerly deemed possible. The close connection 

 between the Reproductive and Nutritive operations, both as regards their re- 

 spective characters, and their dependence upon one another, has long been 

 recognized ; and it is now rendered still more evident. Nutrition has been 

 not unaptly designated "a perpetual reproduction;" and the expression is 

 strictly correct. In the fully-formed organism, the supply of alimentary ma- 

 terial to every part of the fabric enables it to produce a tissue resembling itself; 

 thus we only find true bone produced in continuity with bone, nerve with nerve, 

 muscle with muscle, and so on. Hence it would appear that, when a group 

 of cells has once taken on a particular kind of development, it continues to 

 reproduce itself on the same plan. But in the Reproductive process it is 

 different. A single cell is generated by certain preliminary actions, from 

 which single cell, all those which subsequently compose the embryonic struc- 

 tures, take their origin ; and it is not until a later period, that any distinction 

 of parts can be traced, in the mass of vesicles which spring from it. Hence 

 the essential character of the process of Reproduction consists in the formation 

 of a cell, which can give origin to others, from which again others spring ; 

 and in the capability of these last to undergo several kinds of transformation, 

 so as ultimately to produce a fabric, in which the number of different parts is 

 equal to that of the functions to be performed, every separate part having a 

 purpose distinct from that of the rest. Such a fabric is considered as a very 

 heterogeneous one; and is eminently distinguished from those homogeneous 

 organisms, in which every part is but a repetition of the rest. Of all Animals, 

 Man possesses, as already shown, the greatest variety of endowments, the 

 greatest number of distinct organs ; and yet Man, in common with the simplest 

 Animal or Plant, takes his origin in a single cell. It is in the almost homo- 

 geneous fabrics of the Cellular Plants, that we find the closest connection be- 

 tween the function of Nutrition and that of Reproduction ; for every one of the 

 vesicles which compose their fabric, is endowed with the power of generating 

 others similar to itself; and these may either extend the parent structure, or 

 separate into new and distinct organisms. Hence it is scarcely possible to 

 draw a line, in these cases, between the Nutrition of the individual, and the 

 Reproduction of the species. 



99. But, it will be inquired, how and where in the Human body (and in the 

 higher Animals in general) is this embryonic vesicle produced, and what are 

 the relative offices of the two sexes in its formation? This is a question 

 which must still be answered with some degree of doubt ; and yet observed 

 phenomena, if explained by the aid of analogy, seem to lead to a very direct 

 conclusion. The embryonic vesicle itself, like other cells, must arise from a 



