ARTERIA INNOMINATA. 



fleeted to the right and left, thus exposing a 

 layer of fascia separating the skin from the 

 platisma muscle ; this fascia is thin externally, 

 but where it corresponds to the interval between 

 the two sterno-mastoid muscles it becomes 

 dense and more or less loaded with fat ; reflect 

 this fascia and the platisma will next appear, 

 behind which is that usually described as the 

 superficial fascia of the neck covering the 

 sterno-mastoid muscle, containing the external 

 jugular vein, and increasing considerably in 

 density above the sternum, over which it passes 

 down in front of the pectoral muscles. Like 

 the previous layer its thickness is augmented 

 by fat. If this be raised the sterno-mastoid 

 muscles and the first layer of the deep cervical 

 fascia, extending between their two anterior 

 margins, are brought into view, together with 

 some small superficial vessels and nerves. 

 This latter fascia should be carefully examined 

 above the sternum to the anterior margin of 

 which it strongly adheres ; it is very dense, so 

 much so that if we endeavour to force a finger 

 into the thorax at this point, it effectually resists 

 our efforts. Behind this fascia is a space cor- 

 responding in depth to the thickness of the 

 upper edge of the first bone of the sternum, 

 containing fat and usually a gland, and in ad- 

 dition a vein rather larger than a crow-quill, 

 extending across the neck about half an inch 

 above the sternum ; this communicates with a 

 vein on either side of the neck running down 

 on the anterior margin of the sterno-mastoid 

 muscle, and should be carefully avoided by 

 the surgeon in the operation for tying the in- 

 nominata, as it is of sufficient size to cause 

 embarrassment if wounded. If the fat and 

 gland be now removed we come down upon 

 the second layer of this fascia, which is also 

 very dense and adheres to the inter-clavicular 

 ligament. Having examined these parts and 

 the triangular space existing between the sternal 

 and clavicular insertions of the sterno-mastoid 

 muscles, the sternal insertions of the latter 

 should be detached and the first bone of the 

 sternum removed ; this will expose the remains 

 of the thymus gland and the sterno-hyoid and 

 thyroid muscles, which being cut through and 

 reflected upwards are found to cover the deep 

 or third layer of the cervical fascia, which 

 may be traced from the anterior scalenus 

 muscle to its union with its fellow of the op- 

 posite side, binding down the cervical vessels, 

 &c. Upon removing this fascia we come down 

 upon the arteria innominata covered by the 

 following parts ; inferiorly the left brachio- 

 cephalic vein passes nearly horizontally across 

 the root of the artery to form the vena cava 

 superior by uniting with the corresponding 

 vein of the right side. Although the com- 

 mencement of the vena cava, strictly speaking, 

 has a closer relation to the arch of the aorta than 

 the innominata, it is nevertheless sufficiently 

 near the latter to render it of considerable im- 

 portance in operations performed upon that 

 vessel. Superiorly the first or upper cardiac 

 nerve in its course towards the thorax crosses 

 the innominata opposite its bifurcation ; we 

 next observe the right inferior thyroid vein, 



851 



which, emanating from the lower portion of 

 the thyroid gland, and having formed with its 

 fellow of the opposite side the thyroid venous 

 plexus runs, obliquely downwards from the 

 gland towards the right side directly in front 

 of the innominata artery, and empties itself 

 into the vena cava superior between the two 

 brachio-cephalic veins. The middle thyroid 

 artery, when it exists, may now be seen ascend- 

 ing in front of the trachea. These several 

 objects, viz. the left brachio-cephalic and thy- 

 roid veins with the cardiac nerve, are all en- 

 veloped in a quantity of loose cellular tissue 

 and glands serving to connect them to the 

 vessel, which may now be fully exposed and 

 its different relations studied; when we shall 

 observe that on its right side there is a space 

 bounded superiorly by the right subclavian 

 artery, inferiorly by the left brachio-cephalic 

 vein, to the right by the right brachio-cephalic 

 vein, and to the left by the innominata artery 

 itself; this is the situation where the aneurismal 

 needle should be introduced in the operation 

 for tying this vessel, as we thus run less risk of 

 wounding the veins. 



From the above description it is evident that 

 the coverings of the innominata may be ar- 

 ranged into ten layers, which, enumerated from 

 the surface, consist of 



1. The skin. 2. Layer of superficial fascia. 

 3. Platisma myoides muscle. 4. Superficial 

 fascia. 5. First bone of the sternum, sternal ex- 

 tremity of the right clavicle, sterno-mastoid 

 muscle, with its accompanying vein the sterno 

 and inter-clavicular ligaments and anterior layer 

 of deep cervical fascia. 6. Cellular tissue, fat, 

 containing large vein and a gland ; the second 

 layer of deep cervical fascia. 7. Sterno-hyoid 

 muscle. 8. Sterno-thyroid muscle. 9. Third 

 layer of deep cervical fascia. 10. Cellular 

 tissue containing the first cardiac nerve, right 

 inferior thyroid, and left brachio-cephalic veins, 

 glands, &c. 



Arrived opposite to the right sterno-clavicu- 

 lar articulation and to the interval between the 

 sternal and clavicular insertions of the sterno- 

 mastoid muscle, the arteria innominata usually 

 divides into the right carotid and subclavian. 

 arteries. It rarely gives off any branches ante- 

 cedent to its division, but a small third branch 

 is frequently observed proceeding from it to 

 distribute itself in front of the trachea, and ter- 

 minate in the thyroid gland. Mr. Harrison, 

 in his work on the Surgical Anatomy of the 

 Arteries, has named it the " middle thyroid 

 artery." The French anatomists give M. 

 Neubauer the credit of discovering it, and 

 consequently term it " 1'artere thyroid ienne de 

 Neubauer " It is, however, as frequently given 

 off from the aorta between the arteria inno- 

 minata and left carotid. 



When we consider the relation which the in- 

 nominata bears to the important organs sur- 

 rounding it, we can scarcely be at any loss to 

 account for the apparently remote symptoms 

 present in aneurism of this vessel; such, for 

 instance, as oedema and blueness of the upper 

 extremities, head and neck, cough, difficulty 

 of breathing and swallowing, vertigo, failure 

 3 K 2 



