A treatise on the blood, inflammation, and gun-shot wounds / by John Hunter ; with notes by James F. Palmer.

  • John Hunter
Date:
1840
Catalogue details

Licence: Public Domain Mark

Credit: A treatise on the blood, inflammation, and gun-shot wounds / by John Hunter ; with notes by James F. Palmer. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    be considered as an elongator muscle to the levalar palpebral, with a disposition to remain relaxed while that muscle is contracted, but contracting when the elevator is tired. The natural contraction of the orbicularis muscle is involuntary, the relaxation, both natural and occasional, is involuntary ; but it has likewise a voluntary con- traction and relaxation, which can be made to exceed the involun- tary, resembling what is inherent in all the sphincters.* Sphincter muscles, as those of the anus and urethra ; and pro- bably the expulsatores seminis, and crura of the diaphragm, have both a voluntary and involuntary contraction. In the two sphincters of the anus and urethra this is evident; and the involuntary con- traction in these muscles I have called sphinctoric. The sphincter ani possesses it to a degree just sufficient to resist the pressure of the air and fasces, while the parts above are inactive, preventing the escape of these, till they give the stimulus for expulsion, and then an involuntary relaxation naturally takes place, similar to what happens in muscular canals. The sphinctoric contraction resembles in its effects that produced by elastic ligaments in other parts of the body, which action may be called contractile elasticity, as bringing back the parts to a certain necessary state, and retaining them there. But elasticity would not here have answered all the purposes, since, as it has no relaxing power, more force would have been required to overcome its resistance in the expulsion of the fasces than the gut above could have been able to exert. But the sustaining power being muscular contraction, a relaxation or cessation of that contraction during the time of expulsion leaves nothing for the fasces to do. but, by means of the action above, simply to dilate the relaxed parts. There is, likewise, in these muscles a still further power of contraction, which is produced by the will, and for the purpose of giving, on particular occasions, greater force than what is commonly necessary. The voluntary action of these muscles is therefore, we find, more power- ful than the involuntary; but upon the whole I think we have reason to suppose that the involuntary muscles are much stronger • * [I see no reason for supposing that the orbicularis is different from the other sphincters, or that it has a disposition to contract peculiar to itself: it is only peculiar in being antagonized by the levator palpebrarum, which is a common voluntary muscle. The tone of muscles, to which may probably be referred the ordinary contraction of the sphincters, is that slight tendency to contract in the longitudinal direction of the fibres by which they adapt themselves to the variety of their situation. Now this tone is in great part lost in the extremities and common sphincters when the nervous supply is cut off, although it seems doubtful in what degree it is dependent on the nerves in common cases, so as to relax when an antagonist muscle comes into play. The tonic retraction of a divided muscle is equally energetic when the nerves which supply that muscle are divided as when they are entire; and fish are more effectually crimped when they are first knocked on the head. The heart of a turtle, recently plucked from the chest and deprived of blood, actively dilates and contracts ; which would lead us to believe that the same action more or less takes place in all the muscles,— the relaxation of a muscle being not merely a cessation of action, but an active dilatation, requiring a stimulus for its production.]