196 NATURE OF SPHERICAL AND OYAL NERVE- CELLS. 



instead of being copies of what I had actually seen, 

 because it is quite certain, from their own representa- 

 tions of the structures seen by them, that they had 

 been studying most imperfect and unsatisfactory 

 specimens. One might fairly expect that before an 

 author ventured to upset the observations of another, 

 he would take proper steps to obtain good prepara- 

 tions. It is, however, quite unnecessary for me to 

 reply to objectors or to try to convince sceptics, as 

 the actual specimen from which my most complex 

 ganglion cell was copied has been examined by a 

 number of observers. 



246. Probable nature f spherical and oval 

 nerve-cells. The oval and spherical cells charac- 

 teristic of the sympathetic, of the ganglia on 

 the posterior roots, &c., are seen at a very early 

 period of development, and the ganglia in which 

 they are found are very large and advanced in deve- 

 lopment as compared with other parts of the nervous 

 system. At a time when these cells are well denned 

 and probably active, the caudate nerve^cells are but 

 small masses of bioplasm which may be easily passed 

 over. In the lower vertebrata, when fully grown, 

 these cells are many times larger than the caudate 

 cells of the spinal cord, and in the ganglia of most 

 invertebrata we find spherical and oval nerve- cells 

 which, I believe, correspond with those under con- 

 sideration. The early development of these .cells and 

 their large size at a time when the caudate nerve- cells 

 are not to be distinguished, their constant presence, 

 their growth and multiplication in the adult and 

 probably at an advanced age, and their peculiar 

 structure at least in some animals their situation 

 as regards the nerves to which they belong, and 

 especially the fact that these are the only cells consti- 

 tuting the nerve-centres upon which the rhythmic 

 contraction of detached portions of the cardiac mus- 

 cular tissue depends, have led me to look upon them 



