CHANGES IN SCIENTIFIC OPINION 19 



period, during which biology gradually grew up 

 and became a separate, well-defined branch of 

 science, a result which was, he thinks, mainly 

 due to the writings of Caspar Friedrich Wolff 

 (1733-1794) and J. F. Blumenbach (1752-1840), 

 and especially of the last named, with whom, 

 as he says, " the old Vitalism reaches its 

 height."* 



What caused the change of opinion with 

 regard to the vitalistic theory which actually 

 took place, for it is, so to speak, only yesterday 

 that hardly a voice was raised anywhere in its 

 favour ? According to Driesch, " the old Vital- End of the 

 ism died literally by a process of self-extermina- old vitalisrr ' 

 tion, for just as political parties are said to 

 perish if they experience no opposition, so may 

 scientific and philosophical theories. From 

 the fact that they are never subject to attack 

 and never expect to be, they cease to be guarded, 

 and new pieces of knowledge which might seem 

 fatal to them, yet might actually be fitted 

 legitimately into their framework, are allowed 

 to rise unheeded until the moment of revolt 

 arises and the worn-out defences, antiquated 



* Only so much of the history of the subject as is neces- 

 sary to make the rest of this book intelligible will be given 

 hej*e. For fuller details readers may be referred to Driesch, 

 The History and Theory of Vitalism: London, Macmillan, 

 1914 (Ref. Driesch. Hist.) which deals with the history- 

 omitting the scholastics with great completeness ; and * 

 M'Dougal, Body and Mind: London, Methuen, 1911). 



