118 THE ELEMENTARY NERVOUS SYSTEM 



papers will find it by no means easy to separate in them 

 fact from speculation and, consequently, it is difficult to 

 state in exact terms Apathy's real contribution to this 

 subject ; but, however this may be, it is certainly true that 

 the appearance of his publications excited others to a 

 further investigation of the subject with the result that 

 nerve-nets were proved to exist in a number of animals. 



As already stated, they 

 were definitely identified by 

 Bethe (1903) in jellyfishes, 

 by Wolff (1904) and by 

 Hadzi (1909) in hydro- 

 zoans, and by Groselj 

 (1909) in sea-anemones. In 

 fact, the coelenterate nerv- 



Fio. 36. Nerve network from a small j i 



blood-vessel in the .palate of the frog. OUS System Seemed LO DC 

 (After Prentiss,.1904.) ., . ' , 



nothing but a nerve-net. 



Evidence was soon brought together to show that 

 nerve-nets were at least components of the nervous sys- 

 tems of echinoderms, worms, arthropods, molluscs, 

 and even vertebrates, where they were especially asso- 

 ciated with the digestive tract and the circulatory sys- 

 tem (Fig. 36), including the heart. Thus nerve-nets 

 were identified from the ccelenterates to the vertebrates, 

 and some of the more ardent advocates of this type of 

 nervous organization went so far as to assume that it 

 was the only type of nervous structure really extant and 

 that the evidence of a synaptic system rested upon his- 

 tological artefacts that obscured the real relations of cell 

 to cell. But this extreme position has not been justified 

 by further research. It is now generally admitted that 

 the conceptions of a synaptic system and of a nerve-net 

 are not opposing ideas, but represent two types of nerv- 



