814 



SUBCLAVIAN ARTERIES. 



approximative^ the stature of the skeleton 

 and of the body by measuring one of the cy- 

 lindrical bones; but instead of testing the 

 value of this conclusion by making use of the 

 extreme values, he contents himself with a 

 rough average. It appears, however, that if 

 we take several cylindrical bones having the 

 same length, and compare them with the cor- 

 responding ascertained stature of the skeleton, 

 the extreme statures are very wide apart. 

 Of seven ulnas, for instance, having each the 

 same length (viz. 10 inches, 8 lines), one cor- 

 responded to a stature of 6 feet 1 inch, 

 and another to a stature of only 5 feet 5 

 inches. The difference of 8^ inches shows 

 the possible error which might be committed 

 by trusting to this standard of comparison, 

 and demonstrates its futility. 



The other illustration is afforded by the 

 well-known test of the absolute weight of the 

 foetal lungs. It used to be laid down as a 

 rough average that in still-born mature chil- 

 dren the weight of the lungs was one ounce, 

 and in children that were born alive two 

 ounces. More accurate observation showed 

 that this rough guess was very far from the 

 truth. It was only, however, by the aid of 

 extreme values that the utter worthlessness 

 of this test could be proved. It resulted from 

 the collation of a moderate number of ob- 

 servations that the losvest weight before and 

 after respiration were the same to an unit, 

 while the greatest weight of the lungs of still- 

 born children, in two instances, surpassed the 

 greatest weight of the lungs of children born 

 alive. Nothing could more clearly demon 

 strate the insufficiency and invalidity of this 

 test. 



The same general principle which applies 

 to averages applies also to the extremes, 

 namely, that the value of the extremes in- 

 creases with the number of observations from 

 which they are selected. It is obvious, how- 

 ever, that a larger number of facts will be re- 

 quired to arrive at a true extreme value than 

 to obtain a close approximation to the true 

 mean : 10,000 facts, for instance, may give a 

 true mean duration of life for the inhabitants 

 of any country ; but as many millions may 

 not happen to embrace the greatest attainable 

 age. 



The same principles, then, apply both to 

 the mean and to the extreme values derived 

 from observation. To obtain a correct mean 

 or a probable extreme, we must multiply our 

 facts. 



BIBLIOGRAPHY. Gavcirrct, Jules, Principes Ge"- 

 ncraux tie Statistique Mcdicale, ou Developpement 

 des Regies qui doivent pre'sider a sou Emploi. De 

 Morgan, Augustus, Ail Essay on Probabilities and 

 their Application to Life Contingencies and In- 

 surance Offices. Laplace, Essai Philosophique sur 

 les Probabilites. Poisson, Kecherches sur la Proba- 

 bilite des Jugements. Todd, Tu'eedy John, The 

 Book of Analysis, or a new Method of Experience. 

 Quetelet M.A. Sur 1'homme, et le Developpement de 

 sea Facultes. 



(William A. Guy.) 



STATISTICS, VITAL. 



STATISTICS. 



See VITAL 



STOMACH and INTESTINAL CANAL. 



See SUPPLESIENT. 



SUBCLAVIAN ARTERIES (Arterial 

 subclfivite, Lat. ; Artercs sous-clavieres, Fr. ; 

 die Schlusselbein Pulsadern, Germ.). These 

 arteries, two in number, are the great vessels 

 destined to supply the upper extremities with 

 blood. Each passes to the corresponding ex- 

 tremity as a continuous trunk, which in its 

 course gives off numerous collateral branches to 

 the larynx, neck, nervous centres, thorax, c. 

 The subclavian arteries on the right and 

 left sides respectively differ from each other 

 in their origin, length, direction, and in their 

 relations to surrounding parts, differences, 

 however, which occur in the first stage of 

 these vessels only : thus, on the right side, 

 the subclavian artery is derived from the 

 Arteria inuominata, and on the left from the 

 arch of the aorta ; but on both sides alike the 

 lower or outer margin of the first rib marks 

 the termination of each vessel, which, in its 

 further course towards the upper extremity, 

 is designated by the name of Axillary. 



The course of each subclavian artery may, 

 in general terms, be described as representing 

 an arch, the convexity of which looks upwards 

 towards the neck, whilst the concavity has an 

 aspect downwards, and corresponds closely to 

 the apex of the lung. On the right side the 

 extremities of this arch are nearly on the same 

 level, the outer, however, passing a little lower 

 down than the inner; whilst on the left side 

 the reverse obtains, the inner (or cardiac) 

 extremity of the arch of the left subclavian 

 artery, which springs from the aorta, being on 

 a much lower level than the outer. Owing to 

 the difference in the origin of these vessels, 

 the left subclavian artery has a stage within 

 the thorax, which does not belong to the 

 artery of the right side. 



The subclavian artery on each side is ac- 

 companied by a vein of large size ; the direction 

 of the vein is much more transverse than that 

 of the artery, so as to resemble in some 

 respect, as Cruveilhier expresses it, " the cord 

 of the arc which the artery describes:" the 

 subclavian vein is consequently the shorter 

 vessel of the two. 



The course of each subclavian artery may 

 be divided into three stages, to which the ma- 

 jority of anatomists agree in assigning the 

 following limits : 



A first stage comprises that portion of the 

 vessel, from its origin, to the inner, or 

 tracheal edge, of the scalenus anticus 

 muscle. 



A second stage includes so much of the 

 artery as is contained between the sca- 

 leni muscles ; and the 



Third stage extends from the acromial edge 

 of the scalenus anticus muscle to the 

 lower or outer margin of the first rib : 

 at this latter point the axillary artery 

 commences. 



According to some anatomists (as Bichat), 

 the outer margin of the scaleni muscles is 

 the limit between the subclavian and axillary 



