THE CELL-THEORY 243 



with what in Hving beings is called the History of Development, that 

 branch of the investigation of structure which does not concern itself 

 with the mere study of one state of a being — like anatomy — but 

 examines into the manner in which the successive anatomical states 

 are related to, and proceed out of, one another. 



A profound physiologist and thinker, a contemporary and worthy 

 rival of Haller, has beautifully expressed the relation of anatomy, of 

 physiology, and of development (which he calls Generation), in the 

 following words : 



" The relations between anatomy, the doctrine of generation, and 

 physiology, are about these. By anatomy we learn from observatiorT^ 

 the composition and structure of an organized body. We, however, 1 

 are unable to explain this composition and structure ; we only know ; 

 that they are thus, and further than this we know nothing. But now, ^ 

 on the one hand, comes the doctrine of generation, in which that 

 which we know from anatomy historically, is traced to its causes ; on 

 the other hand, we have physiology, in which the actions which an 

 organized body is capable of producing are explained. Physiology is 

 related to anatomy exactly as the corollary to the theorem from which 

 it is deduced ; my theory (of generation) is related to anatomy as its 

 demonstration to the theorem." ^ 



And again we find the relation of development to anatomy 

 admirably and epigrammatically expressed in the ' Theoria Gene- 

 rationis ' of the same writer. Development is, he says, " anatomia 

 rationalis.'' 



It has been said, and without doubt with profound truth, that the 

 study of the structure of living beings originated in the wonder excited 

 by their actions. But though this may, nay, must, have been the case 

 at first, and though the curiosity of man has for three centuries past 

 directed itself, with almost equal impartiality, to physiological, 



of living bodies is not really the result of some external cause with which we are un- 

 acquainted? It might be said, that the apparent absence of change in external conditions, 

 is no more evidence that the vital phenomena are independent of some such causes, than the 

 continuous running of a stream when the dam is opened, independent of any further alteration 

 of external conditions, is evidence of spontaneity. The action of the spermatozoon, e.g., 

 might be compared to the raising of the dam. We have preferred above, however, a vivid 

 to an exact definition of our conception of life, as likely to be more useful. If we were to 

 attempt an exact definition, it would be, that a living being is a natural body which presents 

 phenomena of growth, of change Oi form, and of chemical composition, of a definite nature, 

 and occurring in definite cycles of succession. This definition will separate living beings 

 from all other terrestrial bodies. It separates them from cosmical bodies (nebulae, &c. ) only 

 by the nature of the phenomena which succeed one another ; so true is it that the microcosm 

 and the macrocosm are reflections of one another. 

 ' Wolff: Theorie von der Generation, p. 12. 



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