[Editor's footnote 22: I venture to think that it is not a philosophically correct mode of expression, to speak of indigestion, or of hunger and thirst, as names of ideas. Hunger and thirst are names of definite sensations; and indigestion is a name of a large group of sensations, held together by very complicated laws of causation. If it be objected, that the word indigestion, and even the words hunger and thirst, comprehend in their meaning other elements than the immediate sensations; that the meaning, for instance, of hunger, includes a deficiency of food, the meaning of indigestion a derangement of the functions of the digestive organs; it still remains true that these additional portions of meaning are physical phenomena, and are not our thoughts or ideas of physical phenomena; and must, therefore, in the general partition of human consciousness between sensations and ideas, take their place with the former, and not with the latter.--_Ed._] {60} It is proper to remark, that, beside the internal feelings to which I have hitherto directed the reader's attention, there are others, which might be classed, and considered apart. The blood-vessels, for example, and motion of the blood, constitute an important part of our System, not without feelings of its own; feelings sometimes amounting to states which seriously command our attention. Of the feelings which accompany fever, a portion may reasonably be assigned to the change of action in the blood-vessels. There are states of feeling, very distinguishable, {61} accompanying diseased states of the heart, and of the nervous and arterial systems. Beside the blood and its vessels, the glandular system is an important part of the active organs of the body; not without sensibility, and of course, not without habitual sensations. The same may be said of the system of the absorbents, of the lymphatics, and of the vascular system in general. The state of the nerves and brain, the most wonderful part of our system, is susceptible of changes, and these changes are accompanied with known changes of feeling. There is a class of diseases which go by the name of nervous diseases: and though they are not a very definite class; though it is not even very well ascertained how far any morbid state of the nerves has to do with them; it is not doubtful that in some of those diseases there are peculiar feelings, which ought to be referred to the nerves. The nerves and brain may thus be, not only the organs of sensations, derived from other senses, but organs of sensations, derived from themselves. On this subject we cannot speak otherwise than obscurely, because we have not distinct names for the things which are to be expressed.