394 INNEttVATION. [CHAP. XII. 



a morbid kind, it is necessary to suppose the existence of a more 

 or less exalted polarity of the centre in order to explain the pheno- 

 mena fully. This polar state will continue in many instances even 

 after the primary peripheral irritation has been removed, as in 

 tetanus, or in the convulsions from intestinal irritation ; and we 

 learn from this fact the importance in practice of attending to the 

 state of the nervous centre as well as to the removal of the irritating 

 cause. 



There are other sympathetic phenomena, of the physical kind, in 

 which, however, the nervous system does not appear to take a pro- 

 minent part. Such are the changes which occur in different and 

 distant organs in connexion with a particular period of life, or the 

 development of a particular function. Among these are the phe- 

 nomena of puberty in both sexes ; the enlargement of the mammae 

 in pregnancy. Whatever part the nervous system may take in such 

 changes, it is impossible to account for them by reference to that 

 system only ; they must rather be regarded as phenomena of nutri- 

 tion occurring in harmony with the laws of growth, and therefore 

 affecting the vital fluid more particularly than any part of the 

 system of solid parts. 



Continuity of texture disposes, as is well known, to the extension 

 of a diseased state originating at some one point. So also does 

 contiguity. Phlegmonous inflammation of the areolar tissue, and 

 erysipelas in the skin, spread with great rapidity. Inflammation 

 arising in one of the opposed surfaces of a serous membrane readily 

 attacks the other. These effects have been vaguely assigned to sym- 

 pathy (the continuous and contiguous sympathy of Hunter). But it 

 cannot be supposed that the nervous system takes part in the pro- 

 duction of such phenomena, which ought rather to be ascribed, in 

 the one case, to the continuity of blood-vessels, and, in the other, 

 to contamination either by effused fluids or by morbid blood. 



On the subjects referred to in this chapter, consult Whytt on the Sympathy 

 of the Nerves, an admirable exposition of the phenomena, obscured, however, 

 by his erroneous views respecting the all-pervading influence of the mind 

 upon vital phenomena ; -Hunter on the blood, etc. ; Alison on the Physio- 

 logical Principle of Sympathy, Edinb. Med. Chir. Trans., vol. ii. ; Miiller's 

 Physiology. 



