194 CLOSE OF THE PRE-EVOLUTIONARY PERIOD 



firmly to the morphological attitude. So Leuckart in his 

 reply to Ludwig, so Rathke in a letter to Leuckart published 

 in that reply, so Reichert in his Bericht, so J. V. Carus in his 

 System dcr thierischcn Morphologic? upheld the validity, the 

 independence, of morphological methods. Leuckart and 

 Rathke called attention to the absolute impossibility of 

 explaining by materialistic physiology the unity of plan 

 underlying the diversity of animal form. J. V. Carus, who 

 was convinced of the validity of physiological methods within 

 their proper sphere, drew a sharp distinction between 

 systematics and morphology on the one hand, and physiology 

 on the other. Physiology had nothing to do with the 

 problems of form at all ; its business was to study the 

 physical and chemical processes which lay at the base of all 

 vital activities. Morphology, on its part, had to accept form 

 as something given, and to study the abstract relations of 

 forms to one another. " On this point," he writes, " stress is 

 to be laid, that morphology has to do with animal form as 

 something given by Nature, that though it follows out the 

 changes taking place during the development of an animal 

 and tries to explain them, it does not enquire after the 

 conditions whose necessary and physical consequence this 

 form actually is " (p. 24). He expressed indeed a pious hope 

 (p. 25) that physiology might one day be so far advanced 

 that it could attempt with some hope of success to discover 

 the physico-chemical determinism of form, but this remained 

 with him merely a pious hope. Reichert, in his />V;vV///, 

 applied to the rather wild theorisings of the physiologist 

 Ludvvig the same clear commonsense criticism that he 

 bestowed on the other " atomists." 



It would take too long to describe the great development 

 that materialistic physiology took at this time, and to show 

 how the separation of morphology from physiology, which 

 originally took place away back in the i/th century, had by 

 this time become almost absolute. The years towards the 

 end of the first half of the century marked indeed the 

 beginning of the classical period as well of physiology as of 

 dogmatic materialism. Moleschott and Buchner popularised 

 materialism in Germany in the 'fifties, while Ludwig, du Bois 



1 Leipzig, 1853. 



