Some of the instances of sympathetic sen sations, referred to above, do not admit of an explanation so obvious. The pain over the brow from ice or cold water in the stomach may be referred to irritation of the gastric branches of the vagus, communicated in the medulla oblongata to the fifth ; but why the irritation should be limited to the ophthalmic division of the fifth cannot be accounted for in the present state of our knowledge.
In those sympathetic movements which are of ordinary and normal occurrence, two pro visions seem to be secured, namely, a certain peripheral organisation of the excitor nerve, and a certain central relation between it and the motor nerve. But in those which are of 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 peri pheral irritation has been removed, as in te tanus, 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 prominent part.. Such are the changes which occur in different and distant organs in con nexion with a particular period of life, or the development of a particular function. Among
these are the phenomena of puberty in both sexes ; the enlargement of the niammm in pregnancy. Whatever part the nervous sys tem may take in such changes, it is impos sible to account for them by reference to that system only ; they must rather be regarded, as phenomena of nutrition occurring in har mony with the laws of growth, and there-, fore 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 sympathy (the continuous and contiguous sym pathy of Hunter). But it cannot be supposed that the nervous system takes part in the pro duction of such phenomena, which ought ra ther 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. (R. B. Todd.)