Page:The Principles and Practice of Medicine.djvu/27

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may be limited to change or derangement of a single function. It is more frequently, however, of a complex nature, being made up of derangements of several functions. For example, inflammation comprises an altered condition of the blood and of the functions of the nervous and muscular tissues. It has indeed been observed, that the component parts of a disease bear something the same kind of relation to it, as ultimate and proximate elements to a chemical compound. Thus, as a general rule, there are simple or primary derangements of function, which are not susceptible of further analysis or simplification ; these being associated together, constitute- secondary or proximate elements, and by a further combination disease itself. It is therefore desirable, before entering upon the study of disease as a whole, to examine its elementary or constituent parts.

special vital properties of muscular tissue are irritability and tonicity.

IRRITABILITY is manifested under the influence of stimuli in two ways : 1st, by a more or less continuous contraction of the muscular fibre, tonic spasm, or cramp ; 2nd, by alternate contrac- tion and relaxation, clonic spasni^ or convulsion.

1. Irritability excessive. Excessive irritability becomes ap- parent 1st, in the force and power by which a muscle contracts ;