318 SPECIAL PHYSIOLOGY. 



is a similar mysterious phenomenon ; and the constitution which pre- 

 disposes to it, seems to depend on analogous abnormal states, It is 

 chiefly observed in nervous, highly excitable, hysterical females. Its 

 occurrence has been placed beyond a doubt, by the evidence of many 

 observers. Indeed, new mental faculties have appeared to some to 

 have been developed, or to have been aroused from a dormant state, 

 by means of mesmerism. Many remarkable movements and actions 

 may, in such persons, undoubtedly be excited by suggestion; powerful 

 contractions of the limbs may be induced, and even certain movements, 

 impressed by others upon the magnetized individual, may suggest cor- 

 responding ideas in his mind, lead to the performance of further move- 

 ments, and so appear to place the individual under the control of the 

 operator. 



The manifestations of the so-called clairvoyants and spirit-rappers, 

 probably rest upon erroneous explanations of facts. Under impres- 

 sions repeatedly acting on the mind, unusual so-called subjective 

 phenomena may be induced in highly excitable persons, through the 

 medium of the nervous centres. In the delirium of fever or of in- 

 sanity, the thoughts, expressions, and acts of the patient, are often 

 directed by an occasional question or remark made by a bystander ; 

 hence credulous persons may perceive, in the expressions of such in- 

 dividuals, supernatural manifestations ; and similar phenomena are 

 induced by so-called animal magnetism. It usually happens that, in 

 questions of this intricate nature, those are the most dogmatic who, 

 by their previous habits of thought and education, are the least quali- 

 fied for such investigations. No right of opinion upon such difficult 

 questions can be granted to enthusiastic dilletanti, or to the worshippers 

 of a longing desire for notoriety. 



THE NERVOUS SYSTEM AND ITS FUNCTIONS IN ANIMALS. 



The nervous system in animals has already been described (pp. 106 to 112). 

 In the Vertebrata, it is constructed on a plan similar to that of Man, consist- 

 ing of a corebro-spinal system, composed of brain, and spinal cord, with cranial 

 and spinal nerves ; and of a sympathetic system, composed of a double gan- 

 glionated cord, with branches of distribution. In the Mollusca, the nervous 

 system is composed of ganglia scattered through the body, and of nervous 

 cords connecting them, or passing from them, to be distributed to the various 

 parts of the body. In the Molluscoida, there is but a single central ganglion, 

 with branches of distribution. In the Annulosa, there exists a series of ganglia 

 with intervening cords, arranged like a chain on the under surface of the body, 

 and having numerous branches proceeding to the various segments and their 

 appendages. In the Annuloida, as in the Molluscoida, either the ganglionic 

 centre is single, or numerous connected ganglia correspond with the radiated 

 form of the body. In the Coelenterata, the nervous system, when seen, con- 

 sists also of a central ganglionic mass, with nerve trunks proceeding from it. 

 In the Protozoa, no nervous system has been discovered. 



However varied in its anatomical disposition, in different animals, the ner- 

 vous system consists essentially, of a central mass or masses of gray matter, 

 connected, in various ways, with nerve fibres ; many of these, as in the cerebro- 

 spinal axis of the Vertebrata, and in the multi-ganglionated system of the 

 Mollusca and Annulosa, are connecting or commissural between different 

 gray masses ; whilst others form the branches, called nerves, proceeding from 

 the gray matter. Physiologically considered, there can be no doubt, as indeed 



