Practical anatomy: a manual of dissections / by Christopher Heath.

  • Christopher Heath
Date:
1870
Catalogue details

Licence: Public Domain Mark

Credit: Practical anatomy: a manual of dissections / by Christopher Heath. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    The two portions are united at tlieir insertion into the an- terior or outer edge of the bicipital groove of the humerus, the muscle being folded near its insertion, so that the sternal fibres pass behind, and reach higher up the bone, than those from the clavicle. The deeper portion of the insertion is more tendinous than the superficial fibres, which are closely connected with the deltoid. The action of the pectoralis major is to [elevate the shoulder], rotate the humerus inwards, and tlien cross it over the chest, and the upper fibres may slightly assist the deltoid in raising the arm. [If the arm have been elevated, the muscle will pull it down.] If the arm were fixed above the chest, the muscle would drag the trunk upwards, as in climbing. It may also act as an extraordinarj^ muscle of inspiration when the arm is fixed, as is seen in the case of asthmatic persons. [In fractures of the humerus it will draw the fragment to which it is attached inwards.] It is supplied b}^ the external anterior thoracic nerve and parti}'' by the internal anterior thoracic nerve. In very well de- veloped subjects, muscular slips are not unfreqnentl}' found lying at the side of the sternum, and superficial to the pectoralis, with which they may have some connection ; but they are more frequentl}^ continuous with the sterno- mastoid muscle. The Axilla. If the arm is well drawn from the side the boundaries of the axilla or aniipit will be readily seen, and if the skin has not been already removed from the posterior boundary (latissimus dorsi), it should now be turned back. The strong deep fascia will be seen stretching from the pectoralis to the latissimus dorsi, forming the base of the conical space known as the axilla: and the student should again notice that it is impossible to thrust the finger deeply into the space so long as the fascia is stretched by the extension of the arm, but that when the arm is drawn to the side the finger passes into the space, and can feel the axillary artery (if injected), and the head of the humerus partially. The lateral cutaneous branches of the iiUercostal vessels and nerves are to be found behind the border of the pec- toralis major b}' carefully dividing the fascia parallel to the ribs. The first intercostal nerve has no lateral branch, but six lateral branches from the upper nerves (from 2d to 7th) will be found appearing at the side of tlie chest, between the digitations of the serratus magnus. Each