170 The Unity of the Organism 



cells and finding tli.at when thus isolated they were able to 

 develop much as they do normally within the organism. 

 Surely no more conclusive proof that the cells of an organ- 

 ism have a hirge measure of independent life could be asked. 

 Harrison epitomizes this aspect of his results in a very clear- 

 cut paragraph : "The energy of outgrowth is immanent in 

 the nerve cell, and the initial direction of outgrowth is 

 already determined within the cell before the outgrowth 

 actually begins. The formation of the fiber is therefore an 

 act of self differentiation within Roux's definition." ^* 



Do not such discoveries favor unquestionably the view 

 that, in Wilson's way of saying it, "the key to all ultimate 

 biological problems must, in last analysis, be sought in the 

 cell?" Some authors, as for example Oppel, answer with a 

 very positive yes, but I have found nothing in Harrison's 

 writings to enable one to be sure what he would do were he 

 to answer this question by choosing between an unqualified 

 yes and an unqualified no. 



However, discussing the general question of the relative 

 trustworthiness and value of experimental studies of the 

 sort devised by him, and those of the sort by which prob- 

 lems of histogenesis are ordinarily prosecuted, he has ex- 

 pressed views which bear strongly on the question, and 

 which we present in his own language : 



"Why, then, should we, in morphology, be still so domin- 

 ated by the conception of the object as it occurs in nature, 

 the organism as a whole, which to many seems to be a sort 

 of fetisli not to be touched lest it show its displeasure by 

 leading the offender astray? There is no real ground for 

 maintaining this attitude. On the contrary we should en- 

 deavor to extend our experimental analysis wherever pos- 

 sible, recognizing that through study of the abnormal, which 

 consists merely of those combinations of conditions and 

 effects tliat do not ordinarily occur in nature, we have the 

 means of reaching an understanding of the normal, and that 



