TO PHYSIOLOGY AND PATHOLOGY. 13 



to sound ; the vibrations of the air-wave are continued through the organs of hear- 

 ing, and communicated to the auditory nerve. The motion imparted to the mem- 

 brane of the typanurn alters its form and composition as little as those of the mole- 

 cules, which have received a like motion from it. As the eye wearies in a picture 

 gallery, although it receives less light in the same period than it would in the open 

 air, so it is also with the ear. 



FALSE IDEA OF REACTION. 



The false ideas conveyed by a mere verbal term, give occasion to constant mis- 

 conception. This is the case with the word reaction, which merely means an 

 opposing agency, but is used in physiology in a very different sense. We say that 

 the glands react upon an irritant, if the secreting power be increased by any external 

 cause, as is perceptible in a number of the secretions at the time of applying an 

 irritant. One peculiarity of organic bodies is, that the increased activity of the 

 glands does not continue, even if the irritation be kept up ; although it lies in the 

 nature of things that the secretion must cease if there is no matter present capable 

 of affording it, and that it will be again augmented in proportion to the new supply. 

 The action of the irritant is not an action upon the glands, but upon the cause, 

 which equally produces the secretion, so that, in consequence oif the irritation, 

 more matter is secreted at one period than at another. 



Thus, in the tail of a lizard, a metamorphosis and renewal of its molecules is 

 continually going on, and when the tail is cut off, and the cut surfaces are separated, 

 the governing forces act against the separation of the parts by the knife, but no 

 counter action of vital force is exhibited upon the knife. The cut surface of the 

 severed piece of tail is not renewed, but the one which is connected with the 

 organism grows, not in consequence of a reaction, but owing to the continuance 

 of the causes which effect the renewal. The body of the lizard is not integrally 

 renewed, when nutrition is absent. If the tail grow again, the other parts of the 

 body lose a corresponding weight and volume. 



The organic body resembles other bodies in all its conditions ; thus many effects 

 which have been called forth continue, even when the causes which gave rise to 

 them have ceased to act; others are balanced, if the active cause of the disturbance 

 cease, because within the body itself there are forces or causes of resistance at 

 work which uninterruptedly make themselves felt. 

 t - 



VERBAL EXPLANATION NO ADVANCE. 



The very small amount of knowledge we have gained from that period of phy- 

 siology, when it was looked upon as a mere natural philosophy, sufficiently proves 

 that the most comprehensive description of a function of the organic body, as the 

 process of respiration or digestion, or a condition of disease, is not sufficient to 

 impart a knowledge of it, and that the most ingenious combinations contribute 

 nothing to our advance, if they be not sustained by a close and accurate inquiry 

 into facts already observed, and such as yet remain to be brought to light. The 

 imaginative faculty alone does not justify us in losing sight of the original point 

 of view, nor in assuming that a consecutive course of views and opinions is an 

 advance in science, since such a mode of proceeding can only be compared to 

 that of a man revolving in a circle, and seeking to gain the greater number of 

 different points of view. Not that these are immaterial, for they indicate the direc- 

 tion in which we must apply our powers; but the mere description of a condition, 

 as for instance, of a catarrh being an inflammation of the mucus membrance of 

 the nose, must not be regarded as an explanation, or as the termination to our in- 



